Internet DRAFT - draft-denis-aegis-aead
draft-denis-aegis-aead
Network Working Group F. Denis
Internet-Draft Fastly Inc.
Intended status: Informational F. E. R. Scotoni
Expires: 7 December 2022 S. Lucas
Individual Contributor
5 June 2022
The AEGIS family of authenticated encryption algorithms
draft-denis-aegis-aead-05
Abstract
This document describes AEGIS-128L and AEGIS-256, two AES-based
authenticated encryption algorithms designed for high-performance
applications.
Discussion Venues
This note is to be removed before publishing as an RFC.
Source for this draft and an issue tracker can be found at
https://github.com/jedisct1/draft-aegis-aead.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 7 December 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. The AEGIS-128L Algorithm . . . . . . . . . . . . . . . . . . 6
3.1. Authenticated Encryption . . . . . . . . . . . . . . . . 7
3.2. Authenticated Decryption . . . . . . . . . . . . . . . . 8
3.3. The Init Function . . . . . . . . . . . . . . . . . . . . 9
3.4. The Update Function . . . . . . . . . . . . . . . . . . . 10
3.5. The Enc Function . . . . . . . . . . . . . . . . . . . . 11
3.6. The Dec Function . . . . . . . . . . . . . . . . . . . . 12
3.7. The DecPartial Function . . . . . . . . . . . . . . . . . 12
3.8. The Finalize Function . . . . . . . . . . . . . . . . . . 13
4. The AEGIS-256 Algorithm . . . . . . . . . . . . . . . . . . . 13
4.1. Authenticated Encryption . . . . . . . . . . . . . . . . 14
4.2. Authenticated Decryption . . . . . . . . . . . . . . . . 15
4.3. The Init Function . . . . . . . . . . . . . . . . . . . . 16
4.4. The Update Function . . . . . . . . . . . . . . . . . . . 17
4.5. The Enc Function . . . . . . . . . . . . . . . . . . . . 18
4.6. The Dec Function . . . . . . . . . . . . . . . . . . . . 18
4.7. The DecPartial Function . . . . . . . . . . . . . . . . . 19
4.8. The Finalize Function . . . . . . . . . . . . . . . . . . 20
5. Encoding (ct, tag) Tuples . . . . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Normative References . . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 23
A.1. AESRound Test Vector . . . . . . . . . . . . . . . . . . 23
A.2. AEGIS-128L Test Vectors . . . . . . . . . . . . . . . . . 23
A.2.1. Update Test Vector . . . . . . . . . . . . . . . . . 23
A.2.2. Test Vector 1 . . . . . . . . . . . . . . . . . . . . 24
A.2.3. Test Vector 2 . . . . . . . . . . . . . . . . . . . . 24
A.2.4. Test Vector 3 . . . . . . . . . . . . . . . . . . . . 24
A.2.5. Test Vector 4 . . . . . . . . . . . . . . . . . . . . 24
A.2.6. Test Vector 5 . . . . . . . . . . . . . . . . . . . . 25
A.2.7. Test Vector 6 . . . . . . . . . . . . . . . . . . . . 25
A.2.8. Test Vector 7 . . . . . . . . . . . . . . . . . . . . 26
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A.2.9. Test Vector 8 . . . . . . . . . . . . . . . . . . . . 26
A.2.10. Test Vector 9 . . . . . . . . . . . . . . . . . . . . 26
A.3. AEGIS-256 Test Vectors . . . . . . . . . . . . . . . . . 27
A.3.1. Update Test Vector . . . . . . . . . . . . . . . . . 27
A.3.2. Test Vector 1 . . . . . . . . . . . . . . . . . . . . 27
A.3.3. Test Vector 2 . . . . . . . . . . . . . . . . . . . . 27
A.3.4. Test Vector 3 . . . . . . . . . . . . . . . . . . . . 28
A.3.5. Test Vector 4 . . . . . . . . . . . . . . . . . . . . 28
A.3.6. Test Vector 5 . . . . . . . . . . . . . . . . . . . . 29
A.3.7. Test Vector 6 . . . . . . . . . . . . . . . . . . . . 29
A.3.8. Test Vector 7 . . . . . . . . . . . . . . . . . . . . 29
A.3.9. Test Vector 8 . . . . . . . . . . . . . . . . . . . . 30
A.3.10. Test Vector 9 . . . . . . . . . . . . . . . . . . . . 30
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
This document describes the AEGIS-128L and AEGIS-256 authenticated
encryption with associated data (AEAD) algorithms [AEGIS], which were
chosen as additional finalists for high-performance applications in
the Competition for Authenticated Encryption: Security,
Applicability, and Robustness (CAESAR). Whilst AEGIS-128 was
selected as a winner for this use case, AEGIS-128L has a better
security margin alongside improved performance and AEGIS-256 uses a
256-bit key [LIMS21]. All variants of AEGIS are constructed from the
AES encryption round function [FIPS-AES]. This document specifies:
* AEGIS-128L, which has a 128-bit key, a 128-bit nonce, a 1024-bit
state, a 128-bit authentication tag, and processes 256-bit input
blocks.
* AEGIS-256, which has a 256-bit key, a 256-bit nonce, a 768-bit
state, a 128-bit authentication tag, and processes 128-bit input
blocks.
The AEGIS cipher family offers performance that significantly exceeds
that of AES-GCM with hardware support for parallelizable AES block
encryption [AEGIS]. Similarly, software implementations can also be
faster, although to a lesser extent.
Unlike with AES-GCM, nonces can be safely chosen at random with no
practical limit when using AEGIS-256. AEGIS-128L also allows for
more messages to be safely encrypted when using random nonces.
With some existing AEAD schemes, such as AES-GCM, an attacker can
generate a ciphertext that successfully decrypts under multiple
different keys (a partitioning oracle attack) [LGR21]. This ability
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to craft a (ciphertext, authentication tag) pair that verifies under
multiple keys significantly reduces the number of required
interactions with the oracle in order to perform an exhaustive
search, making it practical if the key space is small. For example,
with password-based encryption, an attacker can guess a large number
of passwords at a time by recursively submitting such a ciphertext to
an oracle, which speeds up a password search by reducing it to a
binary search.
A key-committing AEAD scheme is more resistant against partitioning
oracle attacks than non-committing AEAD schemes, making it
significantly harder to find multiple keys that are valid for a given
authentication tag. As of the time of writing, no research has been
published claiming that AEGIS is not a key-committing AEAD scheme.
Finally, unlike most other AES-based AEAD constructions, such as
Rocca and Tiaoxin, leaking the state does not leak the key.
Note that an earlier version of Hongjun Wu and Bart Preneel's paper
introducing AEGIS specified AEGIS-128L and AEGIS-256 sporting
differences with regards to the computation of the authentication tag
and the number of rounds in Finalize() respectively. We follow the
specification of [AEGIS] that is current at the time of writing,
which can be found in the References section of this document.
2. Conventions and Definitions
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
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Primitives:
* |x|: the length of x in bits.
* a ^ b: the bitwise exclusive OR operation between a and b.
* a & b: the bitwise AND operation between a and b.
* a || b: the concatenation of a and b.
* a mod b: the remainder of the Euclidean division between a as the
dividend and b as the divisor.
* LE64(x): the little-endian encoding of 64-bit integer x.
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* Pad(x, n): padding operation. Trailing zeros are concatenated to
x until the total length is a multiple of n bits.
* Truncate(x, n): truncation operation. The first n bits of x are
kept.
* Split(x, n): splitting operation. x is split into n-bit blocks,
ignoring partial blocks.
* Tail(x, n): returns the last n bits of x.
* AESRound(in, rk): a single round of the AES encryption round
function, which is the composition of the SubBytes, ShiftRows,
MixColums and AddRoundKey transformations, as defined in section 5
of [FIPS-AES]. Here, in is the 128-bit AES input state, and rk is
the 128-bit round key.
* Repeat(n, F): n sequential evaluations of the function F.
* CtEq(a, b): compares a and b in constant-time, returning True for
an exact match, False otherwise.
AEGIS internal functions:
* Update(M0, M1): the state update function.
* Init(key, nonce): the initialization function.
* Enc(xi): the input block encryption function.
* Dec(ci): the input block decryption function.
* DecPartial(cn): the input block decryption function for the last
ciphertext bits when they do not fill an entire block.
* Finalize(ad_len, msg_len): the authentication tag generation
function.
Input blocks are 256 bits for AEGIS-128L and 128 bits for AEGIS-256.
AES blocks:
* Si: the i-th AES block of the current state.
* S'i: the i-th AES block of the next state.
* {Si, ...Sj}: the vector of the i-th AES block of the current state
to the j-th block of the current state.
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* C0: the constant 0x000101020305080d1522375990e97962 as an AES
block.
* C1: the constant 0xdb3d18556dc22ff12011314273b528dd as an AES
block.
AES blocks are always 128 bits in length.
Input and output values:
* key: the encryption key (128 bits for AEGIS-128L, 256 bits for
AEGIS-256).
* nonce: the public nonce (128 bits for AEGIS-128L, 256 bits for
AEGIS-256).
* ad: the associated data.
* msg: the plaintext.
* ct: the ciphertext.
* tag: the authentication tag (128 bits).
3. The AEGIS-128L Algorithm
AEGIS-128L has a 1024-bit state, made of eight 128-bit blocks {S0,
...S7}.
The parameters for this algorithm, whose meaning is defined in
[RFC5116], Section 4 are:
* K_LEN (key length) is 16 octets (128 bits).
* P_MAX (maximum length of the plaintext) is 2^61 octets (2^64
bits).
* A_MAX (maximum length of the associated data) is 2^61 octets (2^64
bits).
* N_MIN (minimum nonce length) = N_MAX (maximum nonce length) = 16
octets (128 bits).
* C_MAX (maximum ciphertext length) = P_MAX + tag length = 2^61 + 16
octets (2^64 + 128 bits).
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Distinct associated data inputs, as described in [RFC5116], Section 3
shall be unambiguously encoded as a single input. It is up to the
application to create a structure in the associated data input if
needed.
3.1. Authenticated Encryption
Encrypt(msg, ad, key, nonce)
The Encrypt function encrypts a message and returns the ciphertext
along with an authentication tag that verifies the authenticity of
the message and associated data, if provided.
Security:
* For a given key, the nonce MUST NOT be reused under any
circumstances; doing so allows an attacker to recover the internal
state.
* The key MUST be randomly chosen from a uniform distribution.
Inputs:
* msg: the message to be encrypted (length MUST be less than P_MAX).
* ad: the associated data to authenticate (length MUST be less than
A_MAX).
* key: the encryption key.
* nonce: the public nonce.
Outputs:
* ct: the ciphertext.
* tag: the authentication tag.
Steps:
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Init(key, nonce)
ct = {}
ad_blocks = Split(Pad(ad, 256), 256)
for xi in ad_blocks:
Enc(xi)
msg_blocks = Split(Pad(msg, 256), 256)
for xi in msg_blocks:
ct = ct || Enc(xi)
tag = Finalize(|ad|, |msg|)
ct = Truncate(ct, |msg|)
return ct and tag
3.2. Authenticated Decryption
Decrypt(ct, tag, ad, key, nonce)
The Decrypt function decrypts a ciphertext, verifies that the
authentication tag is correct, and returns the message on success or
an error if tag verification failed.
Security:
* If tag verification fails, the decrypted message and wrong message
authentication tag MUST NOT be given as output. The decrypted
message MUST be overwritten with zeros.
* The comparison of the input tag with the expected_tag MUST be done
in constant time.
Inputs:
* ct: the ciphertext to be decrypted (length MUST be less than
C_MAX).
* tag: the authentication tag.
* ad: the associated data to authenticate (length MUST be less than
A_MAX).
* key: the encryption key.
* nonce: the public nonce.
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Outputs:
* Either the decrypted message msg, or an error indicating that the
authentication tag is invalid for the given inputs.
Steps:
Init(key, nonce)
msg = {}
ad_blocks = Split(Pad(ad, 256), 256)
for xi in ad_blocks:
Enc(xi)
ct_blocks = Split(ct, 256)
cn = Tail(ct, |ct| mod 256)
for ci in ct_blocks:
msg = msg || Dec(ci)
if cn is not empty:
msg = msg || DecPartial(cn)
expected_tag = Finalize(|ad|, |msg|)
if CtEq(tag, expected_tag) is False:
erase msg
return "verification failed" error
else:
return msg
3.3. The Init Function
Init(key, nonce)
The Init function constructs the initial state {S0, ...S7} using the
given key and nonce.
Inputs:
* key: the encryption key.
* nonce: the nonce.
Defines:
* {S0, ...S7}: the initial state.
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Steps:
S0 = key ^ nonce
S1 = C1
S2 = C0
S3 = C1
S4 = key ^ nonce
S5 = key ^ C0
S6 = key ^ C1
S7 = key ^ C0
Repeat(10, Update(nonce, key))
3.4. The Update Function
Update(M0, M1)
The Update function is the core of the AEGIS-128L algorithm. It
updates the state {S0, ...S7} using two 128-bit values.
Inputs:
* M0: the first 128-bit block to be absorbed.
* M1: the second 128-bit block to be absorbed.
Modifies:
* {S0, ...S7}: the state.
Steps:
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S'0 = AESRound(S7, S0 ^ M0)
S'1 = AESRound(S0, S1)
S'2 = AESRound(S1, S2)
S'3 = AESRound(S2, S3)
S'4 = AESRound(S3, S4 ^ M1)
S'5 = AESRound(S4, S5)
S'6 = AESRound(S5, S6)
S'7 = AESRound(S6, S7)
S0 = S'0
S1 = S'1
S2 = S'2
S3 = S'3
S4 = S'4
S5 = S'5
S6 = S'6
S7 = S'7
3.5. The Enc Function
Enc(xi)
The Enc function encrypts a 256-bit input block xi using the state
{S0, ...S7}.
Inputs:
* xi: the 256-bit input block.
Outputs:
* ci: the 256-bit encrypted block.
Steps:
z0 = S6 ^ S1 ^ (S2 & S3)
z1 = S2 ^ S5 ^ (S6 & S7)
t0, t1 = Split(xi, 128)
out0 = t0 ^ z0
out1 = t1 ^ z1
Update(t0, t1)
ci = out0 || out1
return ci
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3.6. The Dec Function
Dec(ci)
The Dec function decrypts a 256-bit input block ci using the state
{S0, ...S7}.
Inputs:
* ci: the 256-bit encrypted block.
Outputs:
* xi: the 256-bit decrypted block.
Steps:
z0 = S6 ^ S1 ^ (S2 & S3)
z1 = S2 ^ S5 ^ (S6 & S7)
t0, t1 = Split(ci, 128)
out0 = t0 ^ z0
out1 = t1 ^ z1
Update(out0, out1)
xi = out0 || out1
return xi
3.7. The DecPartial Function
DecPartial(cn)
The DecPartial function decrypts the last ciphertext bits cn using
the state {S0, ...S7} when they do not fill an entire block.
Inputs:
* cn: the encrypted input.
Outputs:
* xn: the decryption of cn.
Steps:
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z0 = S6 ^ S1 ^ (S2 & S3)
z1 = S2 ^ S5 ^ (S6 & S7)
t0, t1 = Split(Pad(cn, 256), 128)
out0 = t0 ^ z0
out1 = t1 ^ z1
xn = Truncate(out0 || out1, |cn|)
v0, v1 = Split(Pad(xn, 256), 128)
Update(v0, v1)
return xn
3.8. The Finalize Function
Finalize(ad_len, msg_len)
The Finalize function computes a 128-bit tag that authenticates the
message and associated data.
Inputs:
* ad_len: the length of the associated data in bits.
* msg_len: the length of the message in bits.
Outputs:
* tag: the authentication tag.
Steps:
t = S2 ^ (LE64(ad_len) || LE64(msg_len))
Repeat(7, Update(t, t))
tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5 ^ S6
return tag
4. The AEGIS-256 Algorithm
AEGIS-256 has a 768-bit state, made of six 128-bit blocks {S0,
...S5}.
The parameters for this algorithm, whose meaning is defined in
[RFC5116], Section 4 are:
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* K_LEN (key length) is 32 octets (256 bits).
* P_MAX (maximum length of the plaintext) is 2^61 octets (2^64
bits).
* A_MAX (maximum length of the associated data) is 2^61 octets (2^64
bits).
* N_MIN (minimum nonce length) = N_MAX (maximum nonce length) = 32
octets (256 bits).
* C_MAX (maximum ciphertext length) = P_MAX + tag length = 2^61 + 16
octets (2^64 + 128 bits).
Distinct associated data inputs, as described in [RFC5116], Section 3
shall be unambiguously encoded as a single input. It is up to the
application to create a structure in the associated data input if
needed.
4.1. Authenticated Encryption
Encrypt(msg, ad, key, nonce)
The Encrypt function encrypts a message and returns the ciphertext
along with an authentication tag that verifies the authenticity of
the message and associated data, if provided.
Security:
* For a given key, the nonce MUST NOT be reused under any
circumstances; doing so allows an attacker to recover the internal
state.
* The key MUST be randomly chosen from a uniform distribution.
Inputs:
* msg: the message to be encrypted (length MUST be less than M_MAX).
* ad: the associated data to authenticate (length MUST be less than
A_MAX).
* key: the encryption key.
* nonce: the public nonce.
Outputs:
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* ct: the ciphertext.
* tag: the authentication tag.
Steps:
Init(key, nonce)
ct = {}
ad_blocks = Split(Pad(ad, 128), 128)
for xi in ad_blocks:
Enc(xi)
msg_blocks = Split(Pad(msg, 128), 128)
for xi in msg_blocks:
ct = ct || Enc(xi)
tag = Finalize(|ad|, |msg|)
ct = Truncate(ct, |msg|)
return ct and tag
4.2. Authenticated Decryption
Decrypt(ct, tag, ad, key, nonce)
The Decrypt function decrypts a ciphertext, verifies that the
authentication tag is correct, and returns the message on success or
an error if tag verification failed.
Security:
* If tag verification fails, the decrypted message and wrong message
authentication tag MUST NOT be given as output. The decrypted
message MUST be overwritten with zeros.
* The comparison of the input tag with the expected_tag MUST be done
in constant time.
Inputs:
* ct: the ciphertext to be decrypted (length MUST be less than
C_MAX).
* tag: the authentication tag.
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* ad: the associated data to authenticate (length MUST be less than
A_MAX).
* key: the encryption key.
* nonce: the public nonce.
Outputs:
* Either the decrypted message msg, or an error indicating that the
authentication tag is invalid for the given inputs.
Steps:
Init(key, nonce)
msg = {}
ad_blocks = Split(Pad(ad, 128), 128)
for xi in ad_blocks:
Enc(xi)
ct_blocks = Split(Pad(ct, 128), 128)
cn = Tail(ct, |ct| mod 128)
for ci in ct_blocks:
msg = msg || Dec(ci)
if cn is not empty:
msg = msg || DecPartial(cn)
expected_tag = Finalize(|ad|, |msg|)
if CtEq(tag, expected_tag) is False:
erase msg
return "verification failed" error
else:
return msg
4.3. The Init Function
Init(key, nonce)
The Init function constructs the initial state {S0, ...S5} using the
given key and nonce.
Inputs:
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* key: the encryption key.
* nonce: the nonce.
Defines:
* {S0, ...S5}: the initial state.
Steps:
k0, k1 = Split(key, 128)
n0, n1 = Split(nonce, 128)
S0 = k0 ^ n0
S1 = k1 ^ n1
S2 = C1
S3 = C0
S4 = k0 ^ C0
S5 = k1 ^ C1
Repeat(4,
Update(k0)
Update(k1)
Update(k0 ^ n0)
Update(k1 ^ n1)
)
4.4. The Update Function
Update(M)
The Update function is the core of the AEGIS-256 algorithm. It
updates the state {S0, ...S5} using a 128-bit value.
Inputs:
* msg: the block to be absorbed.
Modifies:
* {S0, ...S5}: the state.
Steps:
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S'0 = AESRound(S5, S0 ^ M)
S'1 = AESRound(S0, S1)
S'2 = AESRound(S1, S2)
S'3 = AESRound(S2, S3)
S'4 = AESRound(S3, S4)
S'5 = AESRound(S4, S5)
S0 = S'0
S1 = S'1
S2 = S'2
S3 = S'3
S4 = S'4
S5 = S'5
4.5. The Enc Function
Enc(xi)
The Enc function encrypts a 128-bit input block xi using the state
{S0, ...S5}.
Inputs:
* xi: the input block.
Outputs:
* ci: the encrypted input block.
Steps:
z = S1 ^ S4 ^ S5 ^ (S2 & S3)
Update(xi)
ci = xi ^ z
return ci
4.6. The Dec Function
Dec(ci)
The Dec function decrypts a 128-bit input block ci using the state
{S0, ...S5}.
Inputs:
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* ci: the encrypted input block.
Outputs:
* xi: the decrypted block.
Steps:
z = S1 ^ S4 ^ S5 ^ (S2 & S3)
xi = ci ^ z
Update(xi)
return xi
It returns the 128-bit block out.
4.7. The DecPartial Function
DecPartial(cn)
The DecPartial function decrypts the last ciphertext bits cn using
the state {S0, ...S5} when they do not fill an entire block.
Inputs:
* cn: the encrypted input.
Outputs:
* xn: the decryption of cn.
Steps:
z = S1 ^ S4 ^ S5 ^ (S2 & S3)
t = Pad(ci, 128)
out = t ^ z
xn = Truncate(out, |cn|)
v = Pad(xn, 128)
Update(v)
return xn
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4.8. The Finalize Function
Finalize(ad_len, msg_len)
The Finalize function computes a 128-bit tag that authenticates the
message and associated data.
Inputs:
* ad_len: the length of the associated data in bits.
* msg_len: the length of the message in bits.
Outputs:
* tag: the authentication tag.
Steps:
t = S3 ^ (LE64(ad_len) || LE64(msg_len))
Repeat(7, Update(t))
tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5
return tag
5. Encoding (ct, tag) Tuples
Applications MAY keep the ciphertext and the 128-bit authentication
tag in distinct structures or encode both as a single string.
In the latter case, the tag MUST immediately follow the ciphertext:
combined_ct = ct || tag
6. Security Considerations
AEGIS-256 offers 256-bit message security against plaintext and state
recovery, whereas AEGIS-128L offers 128-bit security. Both have a
128-bit authentication tag, which implies that a given tag may verify
under multiple keys. However, assuming AEGIS is key-committing,
finding equivalent keys is expected to be significantly more
difficult than for authentication schemes based on polynomial
evaluation, such as GCM and Poly1305.
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Under the assumption that the secret key is unknown to the attacker
and the tag is not truncated, both AEGIS-128L and AEGIS-256 target
128-bit security against forgery attacks.
Both algorithms MUST be used in a nonce-respecting setting: for a
given key, a nonce MUST only be used once. Failure to do so would
immediately reveal the bitwise difference between two messages.
If tag verification fails, the decrypted message and wrong message
authentication tag MUST NOT be given as output. As shown in the
analysis of the (robustness of CAESAR candidates beyond their
guarantees)[CRA18], even a partial leak of the plaintext without
verification would facilitate chosen ciphertext attacks.
Every key MUST be randomly chosen from a uniform distribution.
The nonce MAY be public or predictable. It can be a counter, the
output of a permutation, or a generator with a long period.
With AEGIS-128L, random nonces can safely encrypt up to 2^48 messages
using the same key with negligible collision probability.
With AEGIS-256, random nonces can be used with no practical limits.
The security of AEGIS against timing and physical attacks is limited
by the implementation of the underlying AESRound() function. Failure
to implement AESRound() in a fashion safe against timing and physical
attacks, such as differential power analysis, timing analysis or
fault injection attacks, may lead to leakage of secret key material
or state information. The exact mitigations required for timing and
physical attacks also depend on the threat model in question.
Security analyses of AEGIS can be found in Chapter 4 of [AEGIS], in
[Min14], in [ENP19], in [LIMS21], and in [JLD21].
7. IANA Considerations
IANA is requested to assign entries for AEAD_AEGIS128L and
AEAD_AEGIS256 in the AEAD Registry with this document as reference.
8. References
8.1. Normative References
[FIPS-AES] National Institute of Standards and Technology, "Advanced
Encryption Standard (AES)", FIPS PUB 197, November 2001,
<http://csrc.nist.gov/publications/fips/fips197/fips-
197.pdf>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<https://www.rfc-editor.org/rfc/rfc5116>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
8.2. Informative References
[AEGIS] Wu, H. and B. Preneel, "AEGIS: A fast encryption algorithm
(v1.1)", 15 September 2016,
<https://competitions.cr.yp.to/round3/aegisv11.pdf>.
[CRA18] Vaudenay, S. and D. Vizár, "Can Caesar Beat Galois?
Robustness of CAESAR Candidates against Nonce Reusing and
High Data Complexity Attacks", Applied Cryptography and
Network Security. ACNS 2018. Lecture Notes in Computer
Science, vol 10892, pp. 476–494,
DOI 10.1007/978-3-319-93387-0_25, 2018,
<https://doi.org/10.1007/978-3-319-93387-0_25>.
[ENP19] Eichlseder, M., Nageler, M., and R. Primas, "Analyzing the
Linear Keystream Biases in AEGIS", IACR Transactions on
Symmetric Cryptology, 2019(4), pp. 348–368,
DOI 10.13154/tosc.v2019.i4.348-368, 31 January 2020,
<https://doi.org/10.13154/tosc.v2019.i4.348-368>.
[JLD21] Jiao, L., Li, Y., and S. Du, "Guess-and-Determine Attacks
on AEGIS", The Computer Journal,
DOI 10.1093/comjnl/bxab059, 22 May 2021,
<https://doi.org/10.1093/comjnl/bxab059>.
[LGR21] Len, J., Grubbs, P., and T. Ristenpart, "Partitioning
Oracle Attacks", 30th USENIX Security Symposium (USENIX
Security 21), pp. 195–212, 2021,
<https://www.usenix.org/conference/usenixsecurity21/
presentation/len>.
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[LIMS21] Liu, F., Isobe, T., Meier, W., and K. Sakamoto, "Weak Keys
in Reduced AEGIS and Tiaoxin", IACR Transactions on
Symmetric Cryptology, 2021(2), pp. 104–139,
DOI 10.46586/tosc.v2021.i2.104-139, 2021,
<https://eprint.iacr.org/2021/187>.
[Min14] Minaud, B., "Linear Biases in AEGIS Keystream", Selected
Areas in Cryptography. SAC 2014. Lecture Notes in Computer
Science, vol 8781, pp. 290–305,
DOI 10.1007/978-3-319-13051-4_18, 2014,
<https://eprint.iacr.org/2018/292>.
Appendix A. Test Vectors
A.1. AESRound Test Vector
in : 000102030405060708090a0b0c0d0e0f
rk : 101112131415161718191a1b1c1d1e1f
out : 7a7b4e5638782546a8c0477a3b813f43
A.2. AEGIS-128L Test Vectors
A.2.1. Update Test Vector
S0 : 9b7e60b24cc873ea894ecc07911049a3
S1 : 330be08f35300faa2ebf9a7b0d274658
S2 : 7bbd5bd2b049f7b9b515cf26fbe7756c
S3 : c35a00f55ea86c3886ec5e928f87db18
S4 : 9ebccafce87cab446396c4334592c91f
S5 : 58d83e31f256371e60fc6bb257114601
S6 : 1639b56ea322c88568a176585bc915de
S7 : 640818ffb57dc0fbc2e72ae93457e39a
M0 : 033e6975b94816879e42917650955aa0
M1 : 033e6975b94816879e42917650955aa0
After Update:
S0 : 596ab773e4433ca0127c73f60536769d
S1 : 790394041a3d26ab697bde865014652d
S2 : 38cf49e4b65248acd533041b64dd0611
S3 : 16d8e58748f437bfff1797f780337cee
S4 : 69761320f7dd738b281cc9f335ac2f5a
S5 : a21746bb193a569e331e1aa985d0d729
S6 : 09d714e6fcf9177a8ed1cde7e3d259a6
S7 : 61279ba73167f0ab76f0a11bf203bdff
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A.2.2. Test Vector 1
key : 00000000000000000000000000000000
nonce: 00000000000000000000000000000000
ad :
msg : 00000000000000000000000000000000
ct : 41de9000a7b5e40e2d68bb64d99ebb19
tag : f4d997cc9b94227ada4fe4165422b1c8
A.2.3. Test Vector 2
key : 00000000000000000000000000000000
nonce: 00000000000000000000000000000000
ad :
msg :
ct :
tag : 83cc600dc4e3e7e62d4055826174f149
A.2.4. Test Vector 3
key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 0001020304050607
msg : 000102030405060708090a0b0c0d0e0f
101112131415161718191a1b1c1d1e1f
ct : 79d94593d8c2119d7e8fd9b8fc77845c
5c077a05b2528b6ac54b563aed8efe84
tag : cc6f3372f6aa1bb82388d695c3962d9a
A.2.5. Test Vector 4
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key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 0001020304050607
msg : 000102030405060708090a0b0c0d
ct : 79d94593d8c2119d7e8fd9b8fc77
tag : 5c04b3dba849b2701effbe32c7f0fab7
A.2.6. Test Vector 5
key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 000102030405060708090a0b0c0d0e0f
101112131415161718191a1b1c1d1e1f
20212223242526272829
msg : 101112131415161718191a1b1c1d1e1f
202122232425262728292a2b2c2d2e2f
3031323334353637
ct : b31052ad1cca4e291abcf2df3502e6bd
b1bfd6db36798be3607b1f94d34478aa
7ede7f7a990fec10
tag : 7542a745733014f9474417b337399507
A.2.7. Test Vector 6
This test MUST return a "verification failed" error.
key : 10000200000000000000000000000000
nonce: 10010000000000000000000000000000
ad : 0001020304050607
msg :
ct : 79d94593d8c2119d7e8fd9b8fc77
tag : 5c04b3dba849b2701effbe32c7f0fab7
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A.2.8. Test Vector 7
This test MUST return a "verification failed" error.
key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 0001020304050607
msg :
ct : 79d94593d8c2119d7e8fd9b8fc78
tag : 5c04b3dba849b2701effbe32c7f0fab7
A.2.9. Test Vector 8
This test MUST return a "verification failed" error.
key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 0001020304050608
msg :
ct : 79d94593d8c2119d7e8fd9b8fc77
tag : 5c04b3dba849b2701effbe32c7f0fab7
A.2.10. Test Vector 9
This test MUST return a "verification failed" error.
key : 10010000000000000000000000000000
nonce: 10000200000000000000000000000000
ad : 0001020304050607
msg :
ct : 79d94593d8c2119d7e8fd9b8fc77
tag : 6c04b3dba849b2701effbe32c7f0fab8
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A.3. AEGIS-256 Test Vectors
A.3.1. Update Test Vector
S0 : 1fa1207ed76c86f2c4bb40e8b395b43e
S1 : b44c375e6c1e1978db64bcd12e9e332f
S2 : 0dab84bfa9f0226432ff630f233d4e5b
S3 : d7ef65c9b93e8ee60c75161407b066e7
S4 : a760bb3da073fbd92bdc24734b1f56fb
S5 : a828a18d6a964497ac6e7e53c5f55c73
M : b165617ed04ab738afb2612c6d18a1ec
After Update:
S0 : e6bc643bae82dfa3d991b1b323839dcd
S1 : 648578232ba0f2f0a3677f617dc052c3
S2 : ea788e0e572044a46059212dd007a789
S3 : 2f1498ae19b80da13fba698f088a8590
S4 : a54c2ee95e8c2a2c3dae2ec743ae6b86
S5 : a3240fceb68e32d5d114df1b5363ab67
A.3.2. Test Vector 1
key : 00000000000000000000000000000000
00000000000000000000000000000000
nonce: 00000000000000000000000000000000
00000000000000000000000000000000
ad :
msg : 00000000000000000000000000000000
ct : b98f03a947807713d75a4fff9fc277a6
tag : 478f3b50dc478ef7d5cf2d0f7cc13180
A.3.3. Test Vector 2
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key : 00000000000000000000000000000000
00000000000000000000000000000000
nonce: 00000000000000000000000000000000
00000000000000000000000000000000
ad :
msg :
ct :
tag : f7a0878f68bd083e8065354071fc27c3
A.3.4. Test Vector 3
key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050607
msg : 000102030405060708090a0b0c0d0e0f
101112131415161718191a1b1c1d1e1f
ct : f373079ed84b2709faee373584585d60
accd191db310ef5d8b11833df9dec711
tag : 8d86f91ee606e9ff26a01b64ccbdd91d
A.3.5. Test Vector 4
key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050607
msg : 000102030405060708090a0b0c0d
ct : f373079ed84b2709faee37358458
tag : c60b9c2d33ceb058f96e6dd03c215652
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A.3.6. Test Vector 5
key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 000102030405060708090a0b0c0d0e0f
101112131415161718191a1b1c1d1e1f
20212223242526272829
msg : 101112131415161718191a1b1c1d1e1f
202122232425262728292a2b2c2d2e2f
3031323334353637
ct : 57754a7d09963e7c787583a2e7b859bb
24fa1e04d49fd550b2511a358e3bca25
2a9b1b8b30cc4a67
tag : ab8a7d53fd0e98d727accca94925e128
A.3.7. Test Vector 6
This test MUST return a "verification failed" error.
key : 10000200000000000000000000000000
00000000000000000000000000000000
nonce: 10010000000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050607
msg :
ct : f373079ed84b2709faee37358458
tag : c60b9c2d33ceb058f96e6dd03c215652
A.3.8. Test Vector 7
This test MUST return a "verification failed" error.
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key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050607
msg :
ct : f373079ed84b2709faee37358459
tag : c60b9c2d33ceb058f96e6dd03c215652
A.3.9. Test Vector 8
This test MUST return a "verification failed" error.
key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050608
msg :
ct : f373079ed84b2709faee37358458
tag : c60b9c2d33ceb058f96e6dd03c215652
A.3.10. Test Vector 9
This test MUST return a "verification failed" error.
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key : 10010000000000000000000000000000
00000000000000000000000000000000
nonce: 10000200000000000000000000000000
00000000000000000000000000000000
ad : 0001020304050607
msg :
ct : f373079ed84b2709faee37358458
tag : d60b9c2d33ceb058f96e6dd03c215653
Acknowledgments
The AEGIS authenticated encryption algorithm was invented by Hongjun
Wu and Bart Preneel.
The round function leverages the AES permutation invented by Joan
Daemen and Vincent Rijmen. They also authored the Pelican MAC that
partly motivated the design of the AEGIS MAC.
We would like to thank Eric Lagergren and Daniel Bleichenbacher for
catching a broken test vector and Daniel Bleichenbacher for many
helpful suggestions.
Authors' Addresses
Frank Denis
Fastly Inc.
Email: fde@00f.net
Fabio Enrico Renzo Scotoni
Individual Contributor
Email: fabio@esse.ch
Samuel Lucas
Individual Contributor
Email: samuel-lucas6@pm.me
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