| COSE Working Group | J. Schaad |
| Internet-Draft | August Cellars |
| Intended status: Informational | July 20, 2015 |
| Expires: January 21, 2016 |
CBOR Encoded Message Syntax
draft-ietf-cose-msg-02
Concise Binary Object Representation (CBOR) is data format designed for small code size and small message size. There is a need for the ability to have the basic security services defined for this data format. This document specifies how to do signatures, message authentication codes and encryption using this data format.
The source for this draft is being maintained in GitHub. Suggested changes should be submitted as pull requests at <https://github.com/cose-wg/cose-spec>. Instructions are on that page as well. Editorial changes can be managed in GitHub, but any substantial issues need to be discussed on the COSE mailing list.
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This Internet-Draft will expire on January 21, 2016.
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There has been an increased focus on the small, constrained devices that make up the Internet of Things (IOT). One of the standards that has come of of this process is the Concise Binary Object Representation (CBOR). CBOR extended the data model of the JavaScript Object Notation (JSON) by allowing for binary data among other changes. CBOR is being adopted by several of the IETF working groups dealing with the IOT world as their encoding of data structures. CBOR was designed specifically to be both small in terms of messages transport and implementation size as well having a schema free decoder. A need exists to provide basic message security services for IOT and using CBOR as the message encoding format makes sense.
The JOSE working group produced a set of documents [RFC7515][RFC7516][RFC7517][RFC7518] that defined how to perform encryption, signatures and message authentication (MAC) operations for JavaScript Object Notation (JSON) documents and then to encode the results using the JSON format [RFC7159]. This document does the same work for use with the Concise Binary Object Representation (CBOR) [RFC7049] document format. While there is a strong attempt to keep the flavor of the original JOSE documents, two considerations are taken into account:
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].
When the words appear in lower case, their natural language meaning is used.
There currently is no standard CBOR grammar available for use by specifications. While we describe the CBOR structures in prose, they are agumented in the text by the use of the CBOR Data Definition Language (CDDL) [I-D.greevenbosch-appsawg-cbor-cddl]. The use of CDDL is intended to be explanitory. In the event of a conflict between the text and the CDDL grammar, the text is authorative. (Problems may be introduced at a later point because the CDDL grammar is not yet fixed.)
CDDL productions that together define the grammar are interspersed in the document like this:
start = COSE_MSG
The collected CDDL can be extracted from the XML version of this document via the following XPath expression below. (Depending on the XPath evaluator one is using, it may be necessary to deal with > as an entity.)
//artwork[@type='CDDL']/text()
In JSON, maps are called objects and only have one kind of map key: a string. In COSE, we use both strings and integers (both negative and non-negative integers) as map keys, as well as data items to identify specific choices. The integers (both positive and negative) are used for compactness of encoding and easy comparison. (Generally, in this document the value zero is going to be reserved and not used.) Since the work "key" is mainly used in its other meaning, as a cryptographic key, we use the term "label" for this usage of either an integer or a string to identify map keys and choice data items.
The CDLL grammar that defines a type that represents a label is given below:
label = int / tstr
In this document we use the following terminology: [CREF2]JLS: I have not gone through the document to determine what needs to be here yet. We mostly want to grab terms which are used in unusual ways or are not generally understood.
Byte is a synonym for octet.
Key management is used as a term to describe how a key at level n is obtained from level n+1 in encrypted and MACed messages. The term is also used to discuss key life cycle management, this document does not discuss key life cycle operations.
One of the issues that needs to be addressed is a requirement that a standard specify a set of algorithms that are required to be implemented. [CREF3]JLS: It would be possible to extend this section to talk about those decisions which an application needs to think about rather than just talking about MTI algoithms. This is done to promote interoperability as it provides a minimal set of algorithms that all devices can be sure will exist at both ends. However, we have elected not to specify a set of mandatory algorithms in this document.
It is expected that COSE is going to be used in a wide variety of applications and on a wide variety of devices. Many of the constrained devices are going to be setup to used a small fixed set of algorithms, and this set of algorithms may not match those available on a device. We therefore have deferred to the application protocols the decision of what to specify for mandatory algorithms.
Since the set of algorithms in an environment of constrained devices may depend on what the set of devices are and how long they have been in operation, we want to highlight that application protocols will need to specify some type of discovery method of algorithm capabilities. The discovery method may be as simple as requiring preconfiguration of the set of algorithms to providing a discovery method built into the protocol. S/MIME provided a number of different ways to approach the problem:
The COSE_MSG structure is a top level CBOR object that corresponds to the DataContent type in the Cryptographic Message Syntax (CMS) [RFC5652]. This structure allows for a top level message to be sent that could be any of the different security services. The security service is identified within the message.
The COSE_Tagged_MSG CBOR type takes the COSE_MSG and prepends a CBOR tag of TBD1 to the encoding of COSE_MSG. By having both a tagged and untagged version of the COSE_MSG structure, it becomes easy to either use COSE_MSG as a top level object or embedded in another object. The tagged version allows for a method of placing the COSE_MSG structure into a choice, using a consistent tag value to determine that this is a COSE object.
The existence of the COSE_MSG and COSE_Tagged_MSG CBOR data types are not intended to prevent protocols from using the individual security primitives directly. Where only a single service is required, that structure can be used directly.
Each of the top-level security objects use a CBOR map as the base structure. Items in the map at the top level are identified by a label. The type of the value associated with the label is determined by the definition of the label.
The set of labels present in a security object is not restricted to those defined in this document. However, it is not recommended that additional fields be added to a structure unless this is going to be done in a closed environment. When new fields need to be added, it is recommended that a new message type be created so that processing of the field can be ensured. Using an older structure with a new field means that any security properties of the new field will not be enforced. Before a new field is added at the outer level, strong consideration needs to be given to defining a new header field and placing it into the protected headers. Applications should make a determination if non-standardized fields are going to be permitted. It is suggested that libraries allow for an option to fail parsing if non-standardized fields exist, this is especially true if they do not allow for access to the fields in other ways.
A label 'msg_type' is defined to distinguish between the different structures when they appear as part of a COSE_MSG object. [CREF4]JLS: I have moved msg_type into the individual structures. However, they would not be necessary in the cases where a) the security service is known and b) security libraries can setup to take individual structures. Should they be moved back to just appearing if used in a COSE_MSG rather than on the individual structure? [CREF5]JLS: Should we create an IANA registries for the values of msg_type?
Implementations MUST be prepared to find an integer under this label that does not correspond to the values 1 to 3. If this is found then the client MUST stop attempting to parse the structure and fail. The value of 0 is reserved and not to be used. If the value of 0 is found, then clients MUST fail processing the structure. Implementations need to recognize that the set of values might be extended at a later date, but they should not provide a security service based on guesses of what is there.
NOTE: Is there any reason to allow for a marker of a COSE_Key structure and allow it to be a COSE_MSG? Doing so does allow for a security risk, but may simplify the code. [CREF6]JLS: OPEN ISSUE
The CDDL grammar that corresponds to the above is:
COSE_MSG = COSE_Sign /
COSE_encrypt /
COSE_mac
COSE_Tagged_MSG = #6.999(COSE_MSG) ; Replace 999 with TBD1
; msg_type values
msg_type_reserved=0
msg_type_signed=1
msg_type_encrypted=2
msg_type_mac=3
The top level of each of the COSE message structures are encoded as maps. We use an integer to distinguish between the different security message types. By searching for the integer under the label identified by msg_type (which is in turn an integer), one can determine which security message is being used and thus what syntax is for the rest of the elements in the map.
| name | number | comments |
|---|---|---|
| msg_type | 1 | Occurs only in top level messages |
| protected | 2 | Occurs in all structures |
| unprotected | 3 | Occurs in all structures |
| payload | 4 | Contains the content of the structure |
| signatures | 5 | For COSE_Sign - array of signatures |
| signature | 6 | For COSE_signature only |
| ciphertext | 4 | TODO: Should we reuse the same as payload or not? |
| recipients | 9 | For COSE_encrypt and COSE_mac |
| tag | 10 | For COSE_mac only |
The CDDL grammar that provides the label values is:
; message_labels msg_type=1 protected=2 unprotected=3 payload=4 signatures=5 signature=6 ciphertext=4 recipients=9 tag=10
The structure of COSE has been designed to have two buckets of information that are not considered to be part of the payload itself, but are used for holding information about algorithms, keys, or evaluation hints for the processing of the layer. These two buckets are available for use in all of the structures in this document except for keys. While these buckets can be present, they may not all be usable in all instances. For example, while the protected bucket is present for recipient structures, most of the algorithms that are used for recipients do not provide the necessary functionality to provide the needed protection and thus the element is not used.
Both buckets are implemented as CBOR maps. The map key is a 'label' (Section 1.4). The value portion is dependent on the definition for the label. Both maps use the same set of label/value pairs. The integer range for labels has been divided into several sections with a standard range, a private range, and a range that is dependent on the algorithm selected. The defined labels can be found in the 'COSE Header Labels' IANA registry (Section 15.3.
Two buckets are provided for each layer: [CREF7]JLS: A completest version of this grammar would list the options available in the protected and unprotected headers. Do we want to head that direction?
Both of the buckets are optional and are omitted if there are no items contained in the map. The CDDL fragment that describes the two buckets is:
header_map = {+ label => any }
Headers = (
? protected => bstr,
? unprotected => header_map
)
The set of header fields defined in this document are:
The header values indicated by 'crit' can be processed by either the security library code or by an application using a security library, the only requirement is that the field is processed.
This table contains a list of all of the generic header parameters defined in document. In the table is the data value type to be used for CBOR as well as the integer value that can be used as a replacement for the name in order to further decrease the size of the sent item.
| name | label | value | registry | description |
|---|---|---|---|---|
| alg | 1 | int / tstr | COSE Algorithm Registry | Integers are taken from table --POINT TO REGISTRY-- |
| crit | 2 | [+ label] | COSE Header Label Registry | integer values are from -- POINT TO REGISTRY -- |
| cty | 3 | tstr / int | media-types registry | Value is either a media-type or an integer from the media-type registry |
| jku | * | tstr | URL to COSE key object | |
| jwk | * | COSE_Key | contains a COSE key not a JWK key | |
| kid | 4 | bstr | key identifier | |
| nonce | 5 | bstr | Nonce or Initialization Vector (IV) | |
| x5c | * | bstr* | X.509 Certificate Chain | |
| x5t | * | bstr | SHA-1 thumbprint of key | |
| x5t#S256 | * | bstr | SHA-256 thumbprint of key | |
| x5u | * | tstr | URL for X.509 certificate | |
| zip | * | int / tstr | Integers are taken from the table --POINT TO REGISTRY-- |
OPEN ISSUES:
The signature structure allows for one or more signatures to be applied to a message payload. There are provisions for attributes about the content and attributes about the signature to be carried along with the signature itself. These attributes may be authenticated by the signature, or just present. Examples of attributes about the content would be the type of content, when the content was created, and who created the content. Examples of attributes about the signature would be the algorithm and key used to create the signature, when the signature was created, and counter-signatures.
When more than one signature is present, the successful validation of one signature associated with a given signer is usually treated as a successful signature by that signer. However, there are some application environments where other rules are needed. An application that employs a rule other than one valid signature for each signer must specify those rules. Also, where simple matching of the signer identifier is not sufficient to determine whether the signatures were generated by the same signer, the application specification must describe how to determine which signatures were generated by the same signer. Support of different communities of recipients is the primary reason that signers choose to include more than one signature. For example, the COSE_Sign structure might include signatures generated with the RSA signature algorithm and with the Elliptic Curve Digital Signature Algorithm (ECDSA) signature algorithm. This allows recipients to verify the signature associated with one algorithm or the other. (The original source of this text is [RFC5652].) More detailed information on multiple signature evaluation can be found in [RFC5752].
The CDDL grammar for a signature message is:
COSE_Sign = {
msg_type => msg_type_signed,
Headers,
? payload => bstr,
signatures => [+ COSE_signature]
}
The fields is the structure have the following semantics:
We use the values in Table 1 as the labels in the COSE_Sign map. While other labels can be present in the map, it is not generally a recommended practice. The other labels can be either of integer or string type, use of other types SHOULD be treated as an error.
The CDDL grammar structure for a signature is:
COSE_signature = {
Headers,
signature => bstr
}
The fields in the structure have the following semantics:
The COSE structure used to create the byte stream to be signed uses the following CDDL grammar structure:
Sig_structure = [
body_protected: bstr,
sign_protected: bstr,
payload: bstr
]
How to compute a signature:
How to verify a signature:
In addition to performing the signature verification, one must also perform the appropriate checks to ensure that the key is correctly paired with the signing identity and that the appropriate authorization is done.
In this section we describe the structure and methods to be used when doing an encryption in COSE. In COSE, we use the same techniques and structures for encrypting both the plain text and the keys used to protect the text. This is different from the approach used by both [RFC5652] and [RFC7516] where different structures are used for the plain text and for the different key management techniques.
One of the byproducts of using the same technique for encrypting and encoding both the content and the keys using the various key management techniques, is a requirement that all of the key management techniques use an Authenticated Encryption (AE) algorithm. (For the purpose of this document we use a slightly loose definition of AE algorithms.) When encrypting the plain text, it is normal to use an Authenticated Encryption with Additional Data (AEAD) algorithm. For key management, either AE or AEAD algorithms can be used. See Appendix A for more details about the different types of algorithms. [CREF13]Ilari: I don't follow/understand this text
The CDDL grammar structure for encryption is:
COSE_encrypt = {
msg_type=>msg_type_encrypted,
COSE_encrypt_fields
}
COSE_encrypt_fields = (
Headers,
? ciphertext => bstr,
? recipients => [+{COSE_encrypt_fields}]
)
Description of the fields:
A typical encrypted message consists of an encrypted content and an encrypted CEK for one or more recipients. The content-encryption key is encrypted for each recipient. The details of this encryption depends on the key management technique used, but the six generally techniques are:
Section 12 provides details on a number of different key management algorithms and discusses which elements need to be present for each of the key management techniques.
The encryption algorithm for AEAD algorithms is fairly simple. In order to get a consistent encoding of the data to be authenticated, the Enc_structure is used to have canonical form of the AAD.
Enc_structure = [
protected: bstr,
external_aad: bstr
]
In this section we describe the structure and methods to be used when doing MAC authentication in COSE. JOSE used a variant of the signature structure for doing MAC operations and it is restricted to using a single pre-shared secret to do the authentication. [CREF14]JLS: Should this sentence be removed? This document allows for the use of all of the same methods of key management as are allowed for encryption.
When using MAC operations, there are two modes in which it can be used. The first is just a check that the content has not been changed since the MAC was computed. Any of the key management methods can be used for this purpose. The second mode is to both check that the content has not been changed since the MAC was computed, and to use key management to verify who sent it. The key management modes that support this are ones that either use a pre-shared secret, or do static-static key agreement. In both of these cases the entity MACing the message can be validated by a key binding. (The binding of identity assumes that there are only two parties involved and you did not send the message yourself.)
COSE_mac = {
msg_type=>msg_type_mac,
Headers,
? payload => bstr,
tag => bstr,
recipients => [+{COSE_encrypt_fields}]
}
Field descriptions:
MAC_structure = [
protected: bstr,
external_aad: bstr,
payload: bstr
]
How to compute a MAC:
There are only a few changes between JOSE and COSE for how keys are formatted. As with JOSE, COSE uses a map to contain the elements of a key. Those values, which in JOSE are base64url encoded because they are binary values, are encoded as bstr values in COSE.
For COSE we use the same set of fields that were defined in [RFC7517]. [CREF15]JLS: Do we remove this line and just define them ourselves? [CREF16]JLS: We can really simplify the grammar for COSE_Key to be just the kty (the one required field) and the generic item. The reason to do this is that it makes things simpler. The reason not to do this says that we really need to add a lot more items so that a grammar check can be done that is more tightly enforced.
COSE_Key = {
kty => tstr / int,
? key_ops => [+ tstr / int ],
? alg => tstr / int,
? kid => bstr,
* label => values
}
COSE_KeySet = [+COSE_Key]
The element “kty” is a required element in a COSE_Key map. All other elements are optional and not all of the elements listed in [RFC7517] or [RFC7518] have been listed here even though they can all appear in a COSE_Key map.
This document defines a set of common map elements for a COSE Key object. Table 3 provides a summary of the elements defined in this section. There are also a set of map elements that are defined for a specific key type. Key specific elements can be found in Section 13.
| name | label | CBOR type | registry | description |
|---|---|---|---|---|
| kty | 1 | tstr / int | COSE General Values | Identification of the key type |
| key_ops | 4 | [* (tstr/int)] | Restrict set of permissible operations | |
| alg | 3 | tstr / int | COSE Algorithm Values | Key usage restriction to this algorithm |
| kid | 2 | bstr | Key Identification value - match to kid in message | |
| x5u | * | tstr | ||
| x5c | * | bstr* | ||
| x5t | * | bstr | ||
| x5t#S256 | * | bstr | ||
| use | * | tstr | deprecated - don't use |
Only the 'kty' field MUST be present in a key object. All other members may be omitted if their behavior is not needed.
| name | value | description |
|---|---|---|
| sign | 1 | The key is used to create signatures. Requires private key fields. |
| verify | 2 | The key is used for verification of signatures. |
| encrypt | 3 | The key is used for key transport encryption. |
| decrypt | 4 | The key is used for key transport decryption. Requires private key fields. |
| wrap key | 5 | The key is used for key wrapping. |
| unwrap key | 6 | The key is used for key unwrapping. Requires private key fields. |
| key agree | 7 | The key is used for key agreement. |
The following provides a CDDL fragment which duplicates the assignment labels from Table 3 and Table 4.
;key_labels key_kty=1 key_kid=2 key_alg=3 key_ops=4 ;key_ops values key_ops_sign=1 key_ops_verify=2 key_ops_encrypt=3 key_ops_decrypt=4 key_ops_wrap=5 key_ops_unwrap=6 key_ops_agree=7
There are two basic signature algorithm structures that can be used. The first is the common signature with appendix. In this structure, the message content is processed and a signature is produced, the signature is called the appendix. This is the message structure used by our common algorithms such as ECDSA and RSASSA-PSS. (In fact two of the letters in RSASSA-PSS are signature appendix.) The basic structure becomes:
signature = Sign(message content, key)
valid = Verification(message content, key, signature)
The second is a signature with message recovery. (An example of such an algorithm is [TBD].) In this structure, the message content is processed, but part of is included in the siguature. Moving bytes of the message content into the signature allows for an effectively smaller signature, the signature size is still potentially large, but the message content is shrunk. This has implications for systems implementing these algoritms and for applications that use them. The first is that the message content is not fully available until after a signature has been validated. Until that point the part of the message contained inside of the signature is unrecoverable. The second is that the security analysis of the strength of the signature is very much based on the structure of the message content. Messages which are highly predictable require additional randomness to be supplied as part of the signature process, in the worst case it because the same as doing a singature with appendix. Thirdly, in the event that multple signatures are applied to a message, all of the signature algorithms are going to be required to consume the same number of bytes of message content.
signature, message sent = Sign(message content, key)
valid, message content = Verification(message sent, key, signature)
At this time, only signatures with appendixes are defined for use with COSE, however considerable interest has been expressed in using a signature with message recovery algorithm due to the effective size reduction that is possible. Implementations will need to keep this in mind for later possible integration.
ECDSA [DSS] defines a signature algorithm using ECC.
The security strength of the signature is no greater than the minimum of the security strength associated with the bit length of the key and the security strength of the hash function. When a hash function is used that has greater security than is provided by the length of the key, the signature algorithm uses the leftmost keyLength bits of the hash function output.
| name | value | hash | description |
|---|---|---|---|
| ES256 | -7 | SHA-256 | ECDSA w/ SHA-256 |
| ES384 | -8 | SHA-384 | ECDSA w/ SHA-384 |
| ES512 | -9 | SHA-512 | ECDSA w/ SHA-512 |
In order to promote interoperability, it is suggested that SHA-256 be used only with keys of length 256, SHA-384 be used only with keys of length 384 and SHA-512 be used only with keys of length 521. This is aligned with the recommendation in Section 4 of [RFC5480].
The signature algorithm results in a pair of integers (R, S). These integers will be of the same order as length of the key used for the signature process. The signature is encoded by converting the integers into byte strings of the same length as the key size. The length is rounded up to the nearest byte and is left padded with zero bits to get to the correct length. The two integers are then concatenated together to form a byte string that is the resulting signature.
Using the function defined in [RFC3447] the signature is:
Signature = I2OSP(R, n) | I2OSP(S, n)
where n = ceiling(key_length / 8)
On of the issues that needs to be discussed is substitution attacks. There are two different things that can potentially be substituted in this algorithm. Both of these attacks are current theoretical only.
The first substitution attack is changing the curve used to validate the signature, the only requirement is that the order of the key match the length of R and S. It is theoretically possible to use a different curve and get a different result. We current do not have any way to deal with this version of the attack except to restrict the overall set of curves that can be used.
The second substitution attack is to change the hash function that is used to verify the signature. This attack can be mitigated by including the signature algorithm identifier in the data to be signed.
The RSASSA-PSS signature algorithm is defined in [RFC3447].
The RSASSA-PSS signature algorithm is parametized with a hash function, a mask generation function and a salt length (sLen). For this specification, the mask generation function is fixed to be MGF1 as defined in [RFC3447]. It has been recommended that the same hash function be used for hashing the data as well as in the mask generation function, for this specification we following this recommendation. The salt length is the same length as the hash function output.
Three algorithms are defined in this document. These algorithms are: Table 6.
There are no algorithm parameters defined for these signature algorithms. A summary of the algorithm definitions can be found in
| name | value | hash | salt length | description |
|---|---|---|---|---|
| PS256 | -10 | SHA-256 | 32 | RSASSA-PSS w/ SHA-256 |
| PS384 | * | SHA-384 | 48 | RSASSA-PSS w/ SHA-384 |
| PS512 | -11 | SHA-512 | 64 | RSASSA-PSS w/ SHA-512 |
Key size. is there a MUST for 2048? or do we need to specify a minimum here?
Message Authentication Codes (MACs) provide data authentication and integrity protection. They provide either no or very limited data origination. (One cannot, for example, be used to prove the identity of the sender to a third party.)
MAC algorithms can be based on either a block cipher algorithm (i.e. AES-MAC) or a hash algorithm (i.e. HMAC). This document defines a MAC algorithm for each of these two constructions.
The Hash-base Message Authentication Code algorithm (HMAC) [RFC2104][RFC4231] was designed, in part, to deal with the birthday attacks on straight hash functions. The algorithm was also designed to all for new hash algorithms to be directly plugged in without changes to the hash function. The HMAC design process has been vindicated as, while the security of hash algorithms such as MD5 has decreased over time, the security of HMAC combined with MD5 has not yet been shown to be compromised [RFC6151].
For use in constrained environments, we define a set of HMAC algorithms that are truncated. There are currently no known issues when truncating, however the security strength of the message tag is correspondingly reduced in strength. When truncating, the left most tag length bits are kept and transmitted.
| name | value | Hash | Length | description |
|---|---|---|---|---|
| HMAC 256/64 | * | SHA-256 | 64 | HMAC w/ SHA-256 truncated to 8 bytes |
| HMAC 256/256 | 4 | SHA-256 | 256 | HMAC w/ SHA-256 |
| HMAC 384/384 | 5 | SHA-384 | 384 | HMAC w/ SHA-384 |
| HMAC 512/512 | 6 | SHA-512 | 512 | HMAC w/ SHA-512 |
TBD.
There are a set of different algorithms that we can specify here. Which should it be?
| name | value | description |
|---|---|---|
| A128GCM | 1 | AES-GCM mode w/ 128-bit key |
| A192GCM | 2 | AES-GCM mode w/ 192-bit key |
| A256GCM | 3 | AES-GCM mode w/ 256-bit key |
Counter with CBC-MAC (CCM) is a generic authentication encryption block cipher mode defined in [RFC3610]. The CCM mode is combined with the AES block encryption algorithm to define a commonly used content encryption algorithm used in constrainted devices.
The CCM mode has two parameter choices. The first choice is M, the size of the authentication field. The choice of the value for M involves a trade-off between message expansion and the probably that an attacker can undetecably modify a message. The second choice is L, the size of the length field. This value requires a trade-off between the maximum message size and the size of the Nonce.
It is unfortunate that the specification for CCM specified L and M as a count of bytes rather than a count of bits. This leads to possible misunderstandings where AES-CCM-8 is frequently used to refer to a version of CCM mode where the size of the authentication is 64-bits and not 8-bits. These values have traditionally been specified as bit counts rather than byte counts. This document will follow the tradition of using bit counts so that it is easier to compare the different algorithms presented in this document.
We define a matrix of algorithms in this document over the values of L and M. Constrained devices are usually operating in situations where they use short messages and want to avoid doing key management operations. This favors smaller values of M and larger values of L. Less constrained devices do will want to be able to user larger messages and are more willing to generate new keys for every operation. This favors larger values of M and smaller values of L. (The use of a large nonce means that random generation of both the key and the nonce will decrease the chances of repeating the pair on two different messages.)
The following values are used for L:
The following values are used for M:
| name | value | L | M | k | description |
|---|---|---|---|---|---|
| AES-CCM-16-64-128 | A281C | 16 | 64 | 128 | AES-CCM mode 128-bit key, 64-bit tag, 13-byte nonce |
| AES-CCM-16-64-192 | A282C | 16 | 64 | 192 | AES-CCM mode 192-bit key, 64-bit tag, 13-byte nonce |
| AES-CCM-16-64-256 | A283C | 16 | 64 | 256 | AES-CCM mode 256-bit key, 64-bit tag, 13-byte nonce |
| AES-CCM-64-64-128 | A881C | 64 | 64 | 128 | AES-CCM mode 128-bit key, 64-bit tag, 7-byte nonce |
| AES-CCM-64-64-192 | A882C | 64 | 64 | 192 | AES-CCM mode 192-bit key, 64-bit tag, 7-byte nonce |
| AES-CCM-64-64-256 | A883C | 64 | 64 | 256 | AES-CCM mode 256-bit key, 64-bit tag, 7-byte nonce |
| AES-CCM-16-128-128 | A2161C | 16 | 128 | 128 | AES-CCM mode 128-bit key, 128-bit tag, 13-byte nonce |
| AES-CCM-16-128-192 | A2162C | 16 | 128 | 192 | AES-CCM mode 192-bit key, 128-bit tag, 13-byte nonce |
| AES-CCM-16-128-256 | A2163C | 16 | 128 | 256 | AES-CCM mode 256-bit key, 128-bit tag, 13-byte nonce |
| AES-CCM-64-128-128 | A8161C | 64 | 128 | 128 | AES-CCM mode 128-bit key, 128-bit tag, 7-byte nonce |
| AES-CCM-64-128-192 | A8162C | 64 | 128 | 192 | AES-CCM mode 192-bit key, 128-bit tag, 7-byte nonce |
| AES-CCM-64-128-256 | A8163C | 64 | 128 | 256 | AES-CCM mode 256-bit key, 128-bit tag, 7-byte nonce |
M00TODO: Make a determination of which ones get 1-, 2- or 3-byte identifiers. I.e. which ones are going to be popular.
When using AES-CCM the following restrictions MUST be enforced:
[RFC3610] additionally calls out one other consideration of note. It is possible to do a pre-computation attack against the algorithm in cases where the portions encryption content is highly predictable. This reduces the security of the key size by half. Ways to deal with this attack include adding a random portion to the nonce value and/or increasing the key size used. Using a portion of the nonce for a random value will decrease the number of messages that a single key can be used for. Increasing the key size may require more resources in the constrained device. See sections 5 and 10 of [RFC3610] for more information.
See [RFC5869].
Inputs:
| name | hash | context |
|---|---|---|
| HKDF-256 | SHA-256 | XXX |
| HKDF-512 | SHA-512 | XXX |
| name | label | type | description |
|---|---|---|---|
| salt | -20 | bstr | Random salt |
The context information structure is used to ensure that the derived keying material is "bound" to the context of the transaction. The context information structure used here is based on that defined in [SP800-56A]. By using CBOR for the encoding of the context information structure, we automatically get the same type of type and length separation of fields that is obtained by the use of ASN.1. This means that there is no need to encode the lengths for the base elements as it is done by the CBOR encoding.
The context information structure refers to PartyU and PartyV as the two parties which are doing the key derivation. Unless the application protocol defines differently, we assign PartyU to the entity that is creating the message and PartyV to the entity that is receiving the message. This is because we are assuming a set of stand alone store and forward messaging processes.
Application protocols are free to define the roles differently. For example, they could assign the PartyU role to the entity that initiates the connection and allow directly sending multiple messages over the line without changing the role information.
We encode the context specific information using a CBOR array type. The fields in the array are:
COSE_KDF_Context = [
AlgorithmID : int / tstr,
PartyUInfo : [
? nonce : bstr / int,
? identity : bstr,
? other : bstr
],
PartyVInfo : [
? nonce : bstr,
? identity : bstr / tstr,
? other : bstr
],
SuppPubInfo : [
keyDataLength : uint,
? other : bstr
],
? SuppPrivInfo : bstr
]
| name | label | type | description |
|---|---|---|---|
| PartyU identity | -21 | bstr | Party U identity Information |
| PartyU nonce | -22 | bstr / int | Party U provided nonce |
| PartyU other | -23 | bstr | Party U other provided information |
| PartyV identity | -24 | bstr | Party V identity Information |
| PartyV nonce | -25 | bstr / int | Party V provided nonce |
| PartyV other | -26 | bstr | Party V other provided information |
There are a number of different key management methods that can be used in the COSE encryption system. In this section we will discuss each of the key management methods, what fields need to be specified, and which algorithms are defined in this document to deal with each of them.
The names of the key management methods used here are the same as are defined in [RFC7517]. Other specifications use different terms for the key management methods or do not support some of the key management methods.
At the moment we do not have any key management methods that allow for the use of protected headers. This may be changed in the future if, for example, the AES-GCM Key wrap method defined in [RFC7518] were extended to allow for authenticated data. In that event, the use of the 'protected' field, which is current forbidden below, would be permitted.
In direct encryption mode, a shared secret between the sender and the recipient is used as the key. [CREF19]JLS: It would be reasonable to support a shared-secret + KDF that is not PBE for when one has good randomness in the shared-secret. When direct encryption mode is used, it MUST be the only mode used on the message. It is a massive security leak to have both direct encryption and a different key management mode on the same message.
For JOSE, direct encryption key management is the only key management method allowed for doing MACed messages. In COSE, all of the key management methods can be used for MACed messages.
The COSE_encrypt structure for the recipient is organized as follows:
We define two key agreement algorithms that function as direct key algorithms. These algorithms are:
| name | value | KDF | description |
|---|---|---|---|
| direct | -6 | N/A | Direct use of CEK |
| direct+KDF | * | HKDF SHA-256 | Shared secret w/ KDF |
Lifetime, Length, Compromise
In key wrapping mode, the CEK is randomly generated and that key is then encrypted by a shared secret between the sender and the recipient. All of the currently defined key wrapping algorithms for JOSE (and thus for COSE) are AE algorithms. Key wrapping mode is considered to be superior to direct encryption if the system has any capability for doing random key generation. This is because the shared key is used to wrap random data rather than data has some degree of organization and may in fact be repeating the same content.
The COSE_encrypt structure for the recipient is organized as follows:
The AES Key Wrapping algorithm is defined in [RFC3394]. This algorithm uses an AES key to wrap a value that is a multiple of 64-bits, as such it can be used to wrap a key for any of the content encryption algorithms defined in this document. [CREF20]JLS: Do we also want to document the use of RFC 5649 as well? It allows for other sizes of keys that might be used for HMAC - i.e. a 200 bit key. The algorithm exists, but I do not personally know of any standard uses of it. The algorithm requires a single fixed parameter, the initial value. This is fixed to the value specified in Section 2.2.3.1 of [RFC3394]. There are no public parameters that vary on a per invocation basis.
| name | value | key size | description |
|---|---|---|---|
| A128KW | -3 | 128 | AES Key Wrap w/ 128-bit key |
| A192KW | -4 | 192 | AES Key Wrap w/ 192-bit key |
| A256KW | -5 | 256 | AES Key Wrap w/ 256-bit key |
There are no specific security considerations for this algorithm.
Key Encryption mode is also called key transport mode in some standards. Key Encryption mode differs from Key Wrap mode in that it uses an asymmetric encryption algorithm rather than a symmetric encryption algorithm to protect the key. The only current Key Encryption mode algorithm supported is RSAES-OAEP.
The COSE_encrypt structure for the recipient is organized as follows:
| name | value | description |
|---|---|---|
| RSA-OAEP | -2 | RSAES OAEP w/ SHA-256 |
A key size of 2048 bits or larger MUST be used with this algorithm. This key size corresponds roughly to the same strength as provided by a 128-bit symmetric encryption algorithm.
It is highly recommended that checks on the key length be done before starting a decryption operation. One potential denial of service operation is to provide encrypted objects using either abnormally long or oddly sized RSA modulus values. Implementations SHOULD be able to encrypt and decrypt with modulus between 2048 and 16K bits in length.[CREF21]JLS: Is this range we want to specify? Applications can impose additional restrictions on the length of the modulus.
When using the 'Direct Key Agreement' key managment method, the two parties use a key agreement method to create a shared secret. A KDF is then applied to the shared secret to derive a key to be used in protecting the data. This key is normally used as a CEK or MAC key, but could be used for other purposes if more than two layers are in use (see Appendix B).
The most commonly used key agreement algorithm used is Diffie-Hellman, but other variants exist. Since COSE is designed for a store and forward environment rather than an on-line environment, many of the DH variants cannot be used as the receiver of the message cannot provide any key material. One side-effect of this is that perfect forward security is not achievable, a static key will always be used for the receiver of the COSE message.
Two variants of DH that are easily supported are:
In this specification, both variants are specified. This has been done to provide the weak data origination option for use with MAC operations.
When direct key agreement mode is used, it MUST be the only key management mode used on the message and there MUST be only one recipient. This method creates the key directly and that makes it difficult to mix with additional recipients. If multiple recipients are needed, then the version with key wrap (Section 12.5.1) needs to be used.
The COSE_encrypt structure for the recipient is organized as follows:
NOTE: Curves 25519 and Goldilocks are elements at risk.
We define one set of key agreement algorithms structured around Elliptic Curves Diffie-Hellman problem. [CREF22]JLS: Does anybody need pure DH? We define both an ephemeral-static and a static-static version of these algorithms. We allow for multiple curves to be used, it needs to be noted that the math required for the curves as well as the point representation is going to be different. [CREF23]JLS: This could just as easily be done by specifying two different set of algorithm identifiers, one for each of the key formats. I don't believe that we need to set things up by having two different sets of algorithm identifiers for the different keys as the structure of what is represented is going to be the same, just the math and point formats are going to be different. The other "difference" is the question of how the octet string of the shared secret is defined. However, since we don't need to specify either in this document we can defer both of them into their respective documents.
We setup to use two different curve structures for the ECDH algorithms.
As shown in Table 16 we define two ECDH algorithm identifiers for EC direct key agreement. These identifiers are:
The parameter is summarized in
Table 17.These parameters are summarized in
Table 17.
| name | value | KDF | description |
|---|---|---|---|
| ECDH-ES | ECDH-ES | HKDF - SHA-256 | ECDH ES w/ HKDF - generate key directly |
| ECDH-SS | ECDH-SS | HKDF - SHA-256 | ECDH SS w/ HKDF - generate key directly |
| name | label | type | algorithm | description |
|---|---|---|---|---|
| ephemeral key | -1 | COSE_Key | ECDH-ES | Ephemeral Public key for the sender |
| static key | -2 | COSE_Key | ECDH-ES | Static Public key for the sender |
| static key id | -3 | bstr | ECDH-SS | Static Public key identifier for the sender |
M00TODO: Talk about curves and point formats.
| name | key type | value | description |
|---|---|---|---|
| P-256 | EC2 | 1 | NIST P-256 also known as .... |
| P-384 | EC2 | 2 | NIST P-384 also known as .... |
| P-521 | EC2 | 3 | NIST P-512 also known as .... |
| Curve25519 | EC1 | 1 | Provide reference |
| Goldilocks | EC1 | 2 | Provide reference |
Key Agreement with Key Wrapping uses a randomly generated CEK. The CEK is then encrypted using a Key Wrapping algorithm and a key derived from the shared secret computed by the key agreement algorithm.
The COSE_encrypt structure for the recipient is organized as follows:
| name | value | KDF | description |
|---|---|---|---|
| ECDH-ES+A128KW | * | HKDF - SHA-256 | ECDH ES w/ Concat KDF and AES Key wrap w/ 128 bit key |
| ECDH-ES+A192KW | * | HKDF - SHA-256 | ECDH ES w/ Concat KDF and AES Key wrap w/ 192 bit key |
| ECDH-ES+A256KW | * | HKDF - SHA-256 | ECDH ES w/ Concat KDF and AES Key wrap w/ 256 bit key |
| name | value | description |
|---|---|---|
| PBES2-HS256+A128KW | * | PBES2 w/ HMAC SHA-256 and AES Key wrap w/ 128 bit key |
| PBES2-HS384+A192KW | * | PBES2 w/ HMAC SHA-384 and AES Key wrap w/ 192 bit key |
| PBES2-HS512+A256KW | * | PBES2 w/ HMAC SHA-512 and AES Key wrap w/ 256 bit key |
The COSE_Key object defines a way to hold a single key object, it is still required that the members of individual key types be defined. This section of the document is where we define an initial set of members for specific key types.
For each of the key types, we define both public and private members. The public members are what is transmitted to others for their usage. We define private members mainly for the purpose of archival of keys by individuals. However, there are some circumstances where private keys may be distributed by various entities in a protocol. Examples include: Entities which have poor random number generation. Centralized key creation for multi-cast type operations. Protocols where a shared secret is used as a bearer token for authorization purposes.
Keys are identified by the 'kty' member of the COSE_Key object. In this document we define four values for the member.
| name | value | description |
|---|---|---|
| EC1 | 1 | Elliptic Curve Keys w/ X Coordinate only |
| EC2 | 2 | Elliptic Curve Keys w/ X,Y Coordinate pair |
| RSA | 3 | RSA Keys |
| Symmetric | 4 | Symmetric Keys |
Two different key structures are being defined for Elliptic Curve keys. One version uses both an x and a y coordinate, potentially with point compression. This is the traditional EC point representation that is used in [RFC5480]. The other version uses only the x coordinate as the y coordinate is either to be recomputed or not needed for the key agreement operation. An example of this is Curve25519 [I-D.irtf-cfrg-curves].
NOTE: This section represents at risk work depending on the ability to get good references for Curve25519 and Goldilocks.
New versions of ECC have been targeted at variants where only a single value of the EC Point need to be transmitted. This work is currently going on in the IRTF CFRG group.
For EC keys with both coordinates, the 'kty' member is set to 1 (EC1). The members that are defined for this key type are:
For public keys, it is REQUIRED that 'crv' and 'x' be present in the structure. For private keys, it is REQUIRED that 'crv' and 'd' be present in the structure. It is RECOMMENDED that 'x' also be present, but it can be recomputed from the required elements and omitting it saves on space.
| name | key type | value | type | description |
|---|---|---|---|---|
| crv | 1 | -1 | int / tstr | EC Curve identifier - Taken from the COSE General Registry |
| x | 1 | -2 | bstr | X Coordinate |
| d | 1 | -4 | bstr | Private key |
The traditional way of sending EC curves has been to send either both the x and y coordinates, or the x coordinate and a sign bit for the y coordinate. The latter encoding has not been recommend in the IETF due to potential IPR issues with Certicom. However, for operations in constrained environments, the ability to shrink a message by not sending the y coordinate is potentially useful.
For EC keys with both coordinates, the 'kty' member is set to 2 (EC2). The members that are defined for this key type are:
For public keys, it is REQUIRED that 'crv', 'x' and 'y' be present in the structure. For private keys, it is REQUIRED that 'crv' and 'd' be present in the structure. It is RECOMMENDED that 'x' and 'y' also be present, but they can be recomputed from the required elements and omitting them saves on space.
| name | key type | value | type | description |
|---|---|---|---|---|
| crv | 2 | -1 | int / tstr | EC Curve identifier - Taken from the COSE General Registry |
| x | 2 | -2 | bstr | X Coordinate |
| y | 2 | -3 | bstr / bool | Y Coordinate |
| d | 2 | -4 | bstr | Private key |
| name | key type | value | type | description |
|---|---|---|---|---|
| n | 3 | -1 | bstr | Modulus Parameter |
| e | 3 | -2 | int | Exponent Parameter |
| d | 3 | -3 | bstr | Private Exponent Parameter |
| p | 3 | -4 | bstr | First Prime Factor |
| q | 3 | -5 | bstr | Second Prime Factor |
| dp | 3 | -6 | bstr | First Factor CRT Exponent |
| dq | 3 | -7 | bstr | Second Factor CRT Exponent |
| qi | 3 | -8 | bstr | First CRT Coefficient |
| other | 3 | -9 | array | Other Primes Info |
| r | 3 | -10 | bstr | Prime Factor |
| d | 3 | -11 | bstr | Factor CRT Exponent |
| t | 3 | -12 | bstr | Factor CRT Coefficient |
Occasionally it is required that a symmetric key be transported between entities. This key structure allows for that to happen.
For symmetric keys, the 'kty' member is set to 3 (Symmetric). The member that is defined for this key type is:
This key structure contains only private key information, care must be taken that it is never transmitted accidentally. For public keys, there are no required fields. For private keys, it is REQUIRED that 'k' be present in the structure.
| name | key type | value | type | description |
|---|---|---|---|---|
| k | 4 | -1 | bstr | Key Value |
There as been an attempt to limit the number of places where the document needs to impose restrictions on how the CBOR Encoder needs to work. We have managed to narrow it down to the following restrictions:
It is requested that IANA assign a new tag from the “Concise Binary Object Representation (CBOR) Tags” registry. It is requested that the tag be assigned in the 0 to 23 value range.
Tag Value: TBD1
Data Item: COSE_Msg
Semantics: COSE security message.
It is requested that IANA create a new registry entitled “COSE Object Labels Registry”. [CREF29]JLS: Finish the registration process.
This table is initially populated by the table in Table 1.
It is requested that IANA create a new registry entitled “COSE Header Labels”.
The columns of the registry are:
The initial contents of the registry can be found in Table 2. The specification column for all rows in that table should be this document.
Additionally, the label of 0 is to be marked as 'Reserved'.
It is requested that IANA create a new registry entitled “COSE Header Algorithm Labels”.
The columns of the registry are:
The initial contents of the registry can be found in: Table 11, Table 12, Table 17, and Appendix D. The specification column for all rows in that table should be this document.
It is requested that IANA create a new registry entitled “COSE Algorithm Registry”.
The initial contents of the registry can be found in the following: Table 9, Table 8, Table 5, Table 7, Table 13, Table 14, Table 15. The specification column for all rows in that table should be this document.
It is requested that IANA create a new registry entitled “COSE Key Map Registry”.
The columns of the registry are:
This registry will be initially populated by the values in Section 7.1. The specification column for all of these entries will be this document.
It is requested that IANA create a new registry “COSE Key Parameters”.
The columns of the table are:
This registry will be initially populated by the values in Table 20, Table 21, Table 22, and Table 23. The specification column for all of these entries will be this document.
This section registers the "application/cose" and "application/cose+cbor" media types in the "Media Types" registry. [CREF30]JLS: Should we register both or just the cose+cbor one? These media types are used to indicate that the content is a COSE_MSG.
This section registers the "application/cose+json" and "application/cose-set+json" media types in the "Media Types" registry. These media types are used to indicate, respectively, that content is a COSE_Key or COSE_KeySet object.
There are security considerations:
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC7049] | Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, October 2013. |
The set of encryption algorithms that can be used with this specification is restricted to authenticated encryption (AE) and authenticated encryption with additional data (AEAD) algorithms. This means that there is a strong check that the data decrypted by the recipient is the same as what was encrypted by the sender. Encryption modes such as counter have no check on this at all. The CBC encryption mode had a weak check that the data is correct, given a random key and random data, the CBC padding check will pass one out of 256 times. There have been several times that a normal encryption mode has been combined with an integrity check to provide a content encryption mode that does provide the necessary authentication. AES-GCM [AES-GCM], AES-CCM [RFC3610], AES-CBC-HMAC [I-D.mcgrew-aead-aes-cbc-hmac-sha2] are examples of these composite modes.
PKCS v1.5 RSA key transport does not qualify as an AE algorithm. There are only three bytes in the encoding that can be checked as having decrypted correctly, the rest of the content can only be probabilistically checked as having decrypted correctly. For this reason, PKCS v1.5 RSA key transport MUST NOT be used with this specification. RSA-OAEP was designed to have the necessary checks that that content correctly decrypted and does qualify as an AE algorithm.
When dealing with authenticated encryption algorithms, there is always some type of value that needs to be checked to see if the authentication level has passed. This authentication value may be:
All of the currently defined Key Management methods only use two levels of the COSE_Encrypt structure. The first level is the message content and the second level is the content key encryption. However, if one uses a key management technique such as RSA-KEM (see Appendix A of RSA-KEM [RFC5990], then it make sense to have three levels of the COSE_Encrypt structure.
These levels would be:
This is an example of what a triple layer message would look like. The message has the following layers:
In effect this example is a decomposed version of using the ECDH-ES+A128KW algorithm.
{
1: 2,
2: h'a10101',
3: {
-1: h'02d1f7e6f26c43d4868d87ce'
},
4: h'64f84d913ba60a76070a9a48f26e97e863e285295a44320878caceb076
3a334806857c67',
9: [
{
3: {
1: -3
},
4: h'5a15dbf5b282ecb31a6074ee3815c252405dd7583e078188',
9: [
{
3: {
1: "ECDH-ES",
5: h'6d65726961646f632e6272616e64796275636b406275636b
6c616e642e6578616d706c65',
4: {
1: 1,
-1: 4,
-2: h'b2add44368ea6d641f9ca9af308b4079aeb519f11e9b8
a55a600b21233e86e68',
-3: h'1a2cf118b9ee6895c8f415b686d4ca1cef362d4a7630a
31ef6019c0c56d33de0'
}
}
}
]
}
]
}
The examples can be found at https://github.com/cose-wg/Examples. I am currently still in the process of getting the examples up there along with some control information for people to be able to check and reproduce the examples.
Examples may have some features that are in questions but not yet incorporated in the document.
To make it easier to read, the examples are presented using the CBOR's diagnostic notation rather than a binary dump. [CREF31]JLS: Do we want to keep this as diagnostic notation or should we switch to having "binary" examples instead? Using the Ruby based CBOR diagnostic tools at ????, the diagnostic notation can be converted into binary files using the following command line: (install command is?...)
diag2cbor < inputfile > outputfile
The examples can be extracted from the XML version of this docuent via an XPath expression as all of the artwork is tagged with the attribute type='CBORdiag'.
This example users the following:
{
1: 3,
2: h'a1016f4145532d434d41432d3235362f3634',
4: h'546869732069732074686520636f6e74656e742e',
10: h'd9afa663dd740848',
9: [
{
3: {
1: -6,
5: h'6f75722d736563726574'
}
}
]
}
This example uses the following:
{
1: 3,
2: h'a10104',
4: h'546869732069732074686520636f6e74656e742e',
10: h'2ba937ca03d76c3dbad30cfcbaeef586f9c0f9ba616ad67e9205d3857
6ad9930',
9: [
{
3: {
1: "ECDH-SS",
5: h'6d65726961646f632e6272616e64796275636b406275636b6c61
6e642e6578616d706c65',
"spk": {
"kid": "peregrin.took@tuckborough.example"
},
"apu": h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d19558ccf
ec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a58368b01
7e7f2a9e5ce4db5'
}
}
]
}
This example uses the following:
{
1: 3,
2: h'a1016e4145532d3132382d4d41432d3634',
4: h'546869732069732074686520636f6e74656e742e',
10: h'6d1fa77b2dd9146a',
9: [
{
3: {
1: -5,
5: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337'
},
4: h'711ab0dc2fc4585dce27effa6781c8093eba906f227b6eb0'
}
]
}
This example uses the following:
{
1: 3,
2: h'a10104',
4: h'546869732069732074686520636f6e74656e742e',
10: h'7aaa6e74546873061f0a7de21ff0c0658d401a68da738dd8937486519
83ce1d0',
9: [
{
3: {
1: "ECDH-ES+A128KW",
5: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65',
4: {
1: 1,
-1: 5,
-2: h'43b12669acac3fd27898ffba0bcd2e6c366d53bc4db71f909
a759304acfb5e18cdc7ba0b13ff8c7636271a6924b1ac63c02688075b55ef2d61
3574e7dc242f79c3',
-3: h'812dd694f4ef32b11014d74010a954689c6b6e8785b333d1a
b44f22b9d1091ae8fc8ae40b687e5cfbe7ee6f8b47918a07bb04e9f5b1a51a334
a16bc09777434113'
}
},
4: h'1b120c848c7f2f8943e402cbdbdb58efb281753af4169c70d0126c
0d16436277160821790ef4fe3f'
},
{
3: {
1: -2,
5: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
4: h'46c4f88069b650909a891e84013614cd58a3668f88fa18f3852940
a20b35098591d3aacf91c125a2595cda7bee75a490579f0e2f20fd6bc956623bf
de3029c318f82c426dac3463b261c981ab18b72fe9409412e5c7f2d8f2b5abaf7
80df6a282db033b3a863fa957408b81741878f466dcc437006ca21407181a016c
a608ca8208bd3c5a1ddc828531e30b89a67ec6bb97b0c3c3c92036c0cb84aa0f0
ce8c3e4a215d173bfa668f116ca9f1177505afb7629a9b0b5e096e81d37900e06
f561a32b6bc993fc6d0cb5d4bb81b74e6ffb0958dac7227c2eb8856303d989f93
b4a051830706a4c44e8314ec846022eab727e16ada628f12ee7978855550249cc
b58'
},
{
3: {
1: -5,
5: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337'
},
4: h'0b2c7cfce04e98276342d6476a7723c090dfdd15f9a518e7736549
e998370695e6d6a83b4ae507bb'
}
]
}
This example uses the following:
{
1: 2,
2: h'a10101',
3: {
-1: h'c9cf4df2fe6c632bf7886413'
},
4: h'45fce2814311024d3a479e7d3eed063850f3f0b9f3f948677e3ae9869b
cf9ff4e1763812',
9: [
{
3: {
1: "ECDH-ES",
5: h'6d65726961646f632e6272616e64796275636b406275636b6c61
6e642e6578616d706c65',
4: {
1: 1,
-1: 4,
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf05
4e1c7b4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d
924b7e03bf822bb'
}
}
}
]
}
This example uses the following:
{
1: 2,
2: h'a1016e4145532d43434d2d3132382f3634',
3: {
-1: h'8f2720f78dce2737ae61a4fa'
},
4: h'0159973c5d790041cf54be80412b3d12a7be30f6b64193d3bb51dfec',
9: [
{
3: {
1: "dir+kdf",
5: h'6f75722d736563726574',
-10: h'61616262636364646565666667676868'
}
}
]
}
This example uses the following:
{
1: 1,
4: h'546869732069732074686520636f6e74656e742e',
5: [
{
2: h'a20165505333383405581e62696c626f2e62616767696e7340686f
626269746f6e2e6578616d706c65',
6: h'1b22515f96fd798a331c7b156e90bfea7f558ec6de840e05a8e5f4
b7be44ea1451c48517da7fd216c6143898673c232a96937ebcfb88264a58f5995
82d89cf8a4f20ef35fbfcfd2aad46ad8b99ea6425367afd898de1b712d558b0d2
49d6d180d0b1fb7256140ec3553556f3b5b95a49931a75998dfc23ca905efc7d8
e04deeb92d5936c0824e535aa344396f73913d8a65de0010600270ae5df7f5c8d
52ae525a7642d4c4ff9e219acaa52fd933df003be36b9e3c77ced37129d66745e
2a42baa3d0b3f2675cd51ae8a64fd024d126be5396c91b9236fb5f8548d09881b
b5d40a61c0d342bed9fe8058f36b8722b9e8465dc3b8bfa4f2fd138ce186b73e4
082'
}
]
}
This example uses the following:
{
1: 1,
4: h'546869732069732074686520636f6e74656e742e',
5: [
{
2: h'a10129',
3: {
5: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
6: h'028947ac3521f66f2506013007e2cd7b0cb09a209e76ab5b95f751
eb63f5730f1672a282419c49b9653d742577fb6a6cea9ab2e1d4d5d9e786e2240
4760663cc74a1c2c90160af92628e1ebbc3eeba552f757054b691ab17271396b7
ff2d86c100b94a2fce0438c0b50ca70bcdd3074a0f8dc40c2e44e9b26e9093287
b7245ee13171b28ea0f3e291c2cca64aa17f7094aee2be02b5fe5cd2cf343e18c
eec0c763cb76a128df9a9cbfc37b835f6467d98d74505eee1dccc9e6ebf2405ea
1329b41a33eeb13f1bbef3a272e42b3df96cdaea9016663e31ddff4603eb66a88
5c583b53977c1fb9707550717d7387f84616a6670e27d4007b08879109aaf3720
f33'
},
{
3: {
1: -9,
5: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
6: h'0195345953742c6725352a13cdc55402c895133525c9a3b16bb47d
02ca5f57f8a34aebf47298c602a8feb1dd71d1936886f21029a4142abf38c3aa3
94b3597c2f35c01987c801edc7022c8fddacbf25bc8794b9ffb7cb27f9f346ba4
4db6f5c9b60406530f62b378c5da3e7e2259327f4e55f48271873496497724492
d90ba67a4b65112'
}
]
}
This section disappears when we make a decision on password based key management.
| name | algorithm | label | CBOR type | description |
|---|---|---|---|---|
| p2c | PBE | -1 | int | |
| p2s | PBE | -2 | bstr |