Internet DRAFT - draft-aanchal4-ntp-mac
draft-aanchal4-ntp-mac
Internet Engineering Task Force A. Malhotra
Internet-Draft S. Goldberg
Intended status: Standards Track Boston University
Expires: April 28, 2017 October 25, 2016
Message Authentication Codes for the Network Time Protocol
draft-aanchal4-ntp-mac-02
Abstract
The Network Time Protocol (NTP) RFC 5905 [RFC5905] uses a message
authentication code (MAC) to cryptographically authenticate its UDP
packets. Currently, NTP packets are authenticated by appending a
128-bit key to the NTP data, and hashing the result with MD5 to
obtain a 128-bit tag. However, as discussed in [BCK] and [RFC6151],
this is not a secure MAC. As such, this draft considers different
secure MAC algorithms for use with NTP, evaluates their performance,
and recommends the use of CMAC-AES [RFC4493]. We also suggest
deprecating the use of MD5 as defined in [RFC5905] for authenticating
NTP packets.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 28, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Malhotra & Goldberg Expires April 28, 2017 [Page 1]
Internet-Draft MACs for NTP October 2016
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. MAC Algorithms . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Performance Requirements . . . . . . . . . . . . . . . . 3
3.2. Security Requirements . . . . . . . . . . . . . . . . . . 4
4. Performance Results . . . . . . . . . . . . . . . . . . . . . 4
5. Other Hardware Platforms . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6.1. Why is GMAC not suitable for NTP? . . . . . . . . . . . . 7
7. Use HMAC or CMAC instead . . . . . . . . . . . . . . . . . . 9
8. GMAC-SIV - Another Potential MAC Candidate . . . . . . . . . 9
9. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
NTP uses a message authentication code (MAC) to authenticate its
packets. Currently, NTP packets are authenticated by appending a
128-bit key to the NTP data, and hashing the result with MD5 to
obtain a 128-bit tag. However, as discussed in [BCK] and [RFC6151],
this not a secure MAC. As such, this draft considers different
secure MAC algorithms for use with NTP, evaluates their performance,
and recommends the use of CMAC-AES [RFC4493]. We also suggest
deprecating the use of MD5, as defined in [RFC5905], for
authenticating NTP packets.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Malhotra & Goldberg Expires April 28, 2017 [Page 2]
Internet-Draft MACs for NTP October 2016
2. MAC Algorithms
We consider five diverse MAC algorithms, which encompass hash-based
HMAC-MD5 and HMAC-SHA224 [RFC2104], block cipher-based CMAC-AES
[RFC4493], and universal hashing-based Galois MAC (GMAC) [RFC4543]
and Poly1305(ChaCha20) as in section 2.6 of [RFC7539]. For
completeness we also benchmark the legacy MD5(key||message) from
[RFC5905].
+--------------------+----------------------+-----------------------+
| Algorithm | Input Key Length | Output Tag Length |
| | (Bytes) | (Bytes) |
+--------------------+----------------------+-----------------------+
| legacy MD5 | 16 | 16 |
| HMAC-MD5 | 16 | 16 |
| HMAC-SHA224 | 16 | 16 |
| CMAC(AES) | 16 | 16 |
| GMAC(AES) | 16 | 16 |
| Poly1305(ChaCha20) | 32 | 16 |
+--------------------+----------------------+-----------------------+
The choice of algorithms evaluated here is motivated, in part, by
standardization and availablity of their open source implementations.
All algorithms we consider, other than the plain MD5, are
standardized. Four out of five algorithms are at least available in
the OpenSSL library, while Poly1305(ChaCha20) is implemented in
LibreSSL (a fork of OpenSSL) and also in BoringSSL (Google's
implementation of OpenSSL).
The output tag length for HMAC-SHA224 is 28 bytes, but we truncate it
to 16 bytes as in section 4 of [RFC7630] to fit into the NTP packet.
As noted in section 6 of [RFC2104] it is safe to truncate the output
of MACs as long as the truncated length is greater than 80-bits and
not less than half the length of the hash output.
3. Requirements
3.1. Performance Requirements
In order to accurately compute the time, NTP ideally requires MAC
algorithms to have a constant computational latency. However, this
is generally not possible, since latency depends on the CPU load,
temperature, and other uncontrollable factors. Instead, a MAC
algorithm that requires fewer clock cycles for computation is
prefered over one that requires more clock cycles, as this directly
translates to a reduction in jitter (i.e., the variance of the
latency for computing the MAC).
Malhotra & Goldberg Expires April 28, 2017 [Page 3]
Internet-Draft MACs for NTP October 2016
Throughput is another important consideration. NTP servers may have
to deal with thousands of client requests per second. A study [NIST]
on the usage analysis of NIST's NTP stratum 1 servers shows that
these servers cater to 28,000 requests/second on an average, per
server.
Most of the Internet is served by stratum 2 and stratum 3 servers,
some of which are a part of voluntary NTP pool. These machines may
be running old hardware. Generally, while benchmarking MAC
algorithms, several optimization techniques on custom specialized
hardware are used to get the best results. However, for the reason
stated above we choose to benchmark performance on a range of
software and hardware platforms with and without optimizations.
3.2. Security Requirements
There are several more constraints specific to NTP that need to be
taken into account.
1. NTP servers are stateless, i.e. they do not keep per client
state.
2. Per [RFC5905], NTP uses a pre-shared symmetric key. This makes
key management difficult because there is no in-band mechanism
for distributing keys. As such, to simplify key management, some
deployments use the same pre-shared key at many servers
(typically at the same stratum). In other words, the same key is
used for several client/server associations.
3. [RFC5905] also has no in-band mechanism to refresh keys.
4. Performance Results
The NTP header is 48 bytes long. We therefore consider the latency
and throughput for several secure MAC algorithms when computed over
48-byte messages.
We customize the in-built speed utility of OpenSSL-1.0.2g (03 May
2016) version to compute the latency and throughput for each MAC as
shown in the tables below. OpenSSL, however, does not implement
stream-cipher ChaCha20-based Poly1305 MAC algorithm. To speed test
this MAC, we use LibreSSL 2.3.1, a fork of OpenSSL implementation.
OpenSSL and LibreSSL are the most widely used cryptographic libraries
and are used by the current NTP implementations.
Since the introduction of New Instruction (NI) set for hardware
support in Intel chips, certain MACs like CMAC and GMAC have
performance advantage on such machines. Based on this, we perform
Malhotra & Goldberg Expires April 28, 2017 [Page 4]
Internet-Draft MACs for NTP October 2016
two different benchmarks: one with AES-NI enabled and the other with
it disabled. Benchmarks were taken on an x86_64, Intel(R) Xeon(R)
CPU E5-2676 v3 @ 2.40GHz with one core CPU.
This table shows throughput in terms of number of 48-byte NTP payload
processed per second.
+--------------------+-------------+-----------------+
| Algorithm | with AES-NI | without AES-NI |
+--------------------+-------------+-----------------+
| legacy MD5 | 3118K | 3165K |
| HMAC-MD5 | 2742K | 2749K |
| HMAC-SHA224 | 1265K | 1267K |
| CMAC(AES) | 7567K | 4388K |
| GMAC(AES) | 16612K | 4627K |
| Poly1305(ChaCha20) | 2598K | 2398K |
+--------------------+-------------+-----------------+
This table shows latency in terms of number of CPU cycles per byte
(cpb) when processing a 48-byte NTP payload.
+--------------------+-------------+-----------------+
| Algorithm | with AES-NI | without AES-NI |
+--------------------+-------------+-----------------+
| legacy MD5 | 16.0 | 15.7 |
| HMAC-MD5 | 18.2 | 18.1 |
| HMAC-SHA224 | 39.4 | 39.0 |
| CMAC(AES) | 6.6 | 11.3 |
| GMAC(AES) | 3.0 | 10.8 |
| Poly1305(ChaCha20) | 14.4 | 15.0 |
+--------------------+-------------+-----------------+
5. Other Hardware Platforms
We also perform tests on the following ARM CPU cores and
PowerPC(PPC)core with OpenSSL 1.0.2h released May 2016. These cores
are most commonly used in consumer products and Industrial Control
Systems (ICS) components. We select these cores to cover the ARM
architecture versions 5/6 to 8. The results vary depending on the
availability of CPU specific optimizations. For example the used
Cortex-A9 and Cortex-A53 CPU have a NEON unit and OpenSSL can utilize
it to accelerate AES.
1. Freescale/Apple PPC74xx 1.5GHz
2. NXP i.MX6 1GHz (dual core) ARM Cortex-A9
3. Broadcom BCM2837 1.2GHz (quad core) ARM Cortex-A53
Malhotra & Goldberg Expires April 28, 2017 [Page 5]
Internet-Draft MACs for NTP October 2016
4. Marvell 88F6281 1.2GHz 88FR131 (ARMv5te compliant)
The table below shows throughput in terms of number of 48-byte NTP
payload processed per second.
+--------------------+---------+------------+-------------+---------+
| Algorithm | PPC74xx | ARM | ARM Cortex | Marvell |
| | | Cortex-A9 | A-53 | |
+--------------------+---------+------------+-------------+---------+
| legacy MD5 | 600K | 543K | 748K | 383k |
| HMAC-MD5 | 463K | 415K | 864K | 438k |
| HMAC-SHA224 | 276K | 245K | 357K | 150k |
| CMAC(AES) | 576K | 412K | 614K | 246k |
| GMAC(AES) | 681K | 1362K | 2193K | 453k |
| Poly1305(ChaCha20) | 335K | 379K | 580K | 273k |
+--------------------+---------+------------+-------------+---------+
The table below shows latency in terms of number of CPU cycles per
byte (cpb) when processing a 48-byte NTP payload.
+--------------------+---------+------------+-------------+---------+
| Algorithm | PPC74xx | ARM | ARM Cortex | Marvell |
| | | Cortex-A9 | A-53 | |
+--------------------+---------+------------+-------------+---------+
| legacy MD5 | 52.1 | 38.4 | 33.4 | 65.3 |
| HMAC-MD5 | 67.4 | 50.3 | 29.0 | 57.1 |
| HMAC-SHA224 | 113.3 | 85.2 | 70.1 | 166.5 |
| CMAC(AES) | 54.2 | 50.5 | 40.7 | 101.2 |
| GMAC(AES) | 50.0 | 15.3 | 11.4 | 55.1 |
| Poly1305(ChaCha20) | 93.1 | 55.0 | 43.1 | 91.7 |
+--------------------+---------+------------+-------------+---------+
6. Security Considerations
The MD5 (key||message) "message authentication code" specified in
[RFC5905] is vulnerable to length extension attacks, and uses the
insecure MD5 hash function, and therefore MUST be deprecated.
Therefore, we consider hash-based MACs (HMAC-MD5, HMAC-SHA224), and
cipher-based MACs (CMAC-AES, Poly1305 (ChaCha20)). The upper bound
on the security level provided by any MAC against brute-force attacks
is min (key-length, tag-length). The security of these MACs can be
worse but not better than this bound. All MAC algorithms we consider
have comparable key-lengths and output tag-lengths. So the advantage
of an adversary that wishes to forge a MAC is lower-bounded by
1/2^{128}.
Malhotra & Goldberg Expires April 28, 2017 [Page 6]
Internet-Draft MACs for NTP October 2016
Assume that an adversary can obtain a valid MAC for q distinct
messages. Then the table below describes the advantage of an
adversary that wishes to forge a MAC in terms of number of queries
(q) it launches.
+--------------------------+-------------------------------+
| Algorithm | Advantage |
+--------------------------+-------------------------------+
| HMAC-MD5 [MB] | q^2/2^{128} |
| HMAC-SHA224 [BCK] | q^2/2^{224} |
| CMAC(AES)[IK] | q^2/2^{128} |
| GMAC(AES) [IOM] | q^2/2^{128} |
| Poly1305(ChaCha20) [DJB] | {e^{{q^2}/{2^{129}}}}/2^{103} |
+--------------------------+-------------------------------+
Poly1305 can easily handle up to q=2^{64} but security degrades
pretty rapidly after that.
However, the bounds in the table above are somewhat optimistic, for
the following reasons.
1. GMAC has an initialization vector (IV) that [RFC4106] allows to
be 1 <= len(IV) <= 2^{64}-1. Per [RFC4106], implementations are
optimized to handle a 12-octet IV. With a 12-octet IV, the total
number of message invocations is bound to 2^{48}. Moreover, if
the IV is reused even once (for the same secret authentication
key and different input messages), then [Joux] shows that the
secret authetication key can easily be recovered by the
adversary. Notice that this attack is even stronger than a
message forgery because it recovers the authentication key. This
is known as nonce-reuse vulnerability.
2. The other three algorithms evaluated here do not suffer from
nonce reuse vulnerabilities where an adversary can recover the
authentication key if the nonce is reused just once.
3. The table above suggests that for CMAC, the total number of
invocations of the MAC is limited to 2^{64}. However, [NIST-CMAC]
recommends, to be on the safe side, that the total number of
invocations of the block cipher algorithm during the lifetime of
the key is limited to 2^{48}.
6.1. Why is GMAC not suitable for NTP?
[Joux] showed that for GMAC-AES, if the IV is repeated just once,
then the authentication key can be fully recovered. None of the
other algorithms evaluated here have this vulnerability. Thus, for
Malhotra & Goldberg Expires April 28, 2017 [Page 7]
Internet-Draft MACs for NTP October 2016
GMAC-AES to be secure, we need to make sure that IV is never
repeated.
[NIST-GMAC] recommends constructing the 12-byte IV used in GMAC by
concatenating a fixed 4-byte salt value concatenate with a variable
8-byte nonce i.e. IV = ( salt|| nonce). Here salt is an implicit
value established when a session is established, remains fixed for
all exchanges in a session (i.e. for all invocations that use the
same authenication key) between the sender and the receiver.
Meanwhile, the nonce is freshly generated for each authenticated
message.
Because NTP servers do not keep per-client state, the nonce can not
be a sequential value. Instead, this nonce must be randomly
generated 8-bytes value chosen freshly for each authenticated
message. According to birthday bound, the nonce value will be
repeated, with high probability, after 2^{32} messages sent in a
given association. This leads to a repeated IV value and to [Joux]'s
attack. Thus, to prevent repeated nonces, we would need to require
the authentication key to be refreshed for the association after
2^{32} messages.
On one hand, 2^{32} is a lot of queries for an honest client,
assuming that the client queries once per minute (which is NTP's
minimum polling interval [RFC5905]). On the other hand, a man-in-
the-middle (MiTM) can quickly and easily exhaust this number by
replaying old authenticated queries to the NTP server.
The main problem here is that NTP lacks an explict in-band key
refresh mechanism that can be invoked automatically (without operator
intervention). And a key refresh mechanism is unlikely to be adopted
as it would allow denial-of-service (DoS) attacks. The state less
nature makes NTP resilient against DoS attacks.
Even if there was a method by which key-refresh could be performed,
there is an additional problem. An NTP server does not keep per-
client state. Therefore, it cannot keep track of the number of
messages it sent in a given association. One idea is to have the
client keep this state, and then send an authenicated request for a
key refresh. However, a man-in-the-middle could replay old
authenticated queries to the NTP server, and then intercept the
server's' response before they reach the legitimate client. In this
case, the client would never know when to ask for a key refresh.
Alternatively, the server could maintain a global counter (since it
can't afford to keep per client counter). And after 2^{32} messages,
it can refresh the keys with all its clients. However, a man-in-the-
Malhotra & Goldberg Expires April 28, 2017 [Page 8]
Internet-Draft MACs for NTP October 2016
middle could exhaust this number quickly and the server will have to
refresh keys with all the clients very frequently.
Thus, we conclude that a scheme that requires refreshing the key
after 2^{32} client queries is not a good idea at all.
Even in the absence of a man-in-the-middle, there is also the problem
of multiple servers using the same authentication key. The salt
could be used to distinguish IVs across different client/server
associations that use the same authenication key. However, this
brings us back to the original key management problem. One way to
deal with this is to choose the 4-byte salt at random. However, this
gives rise to a birthday bound of 2^{16} = 65,000 unique IVs. If we
consider 20,000 stratum 3 clients synchronizing to three stratum 2
servers each, all of which are in the same organization and share the
same symmetric key, we get very close to the birthday bound. This is
another disadvantage of using GMAC with NTP.
7. Use HMAC or CMAC instead
1. CMAC seems to be the next best choice. Leaving out GMAC, it has
the best performance with and without hardware support. It is
not vulnerable to nonce misuse issues.
2. HMACs are inherently slower because of their structure and also
in some cases because of lack of built-in hardware support.
3. On the other hand, it is much easier to get the right
implementation for HMAC compared to CMAC.
8. GMAC-SIV - Another Potential MAC Candidate
GMAC-SIV is another possible MAC candidate, which claims to be nonce-
misuse resistant [SIV]. There is an IETF Internet draft for the
standardization of GCM-SIV AEAD mode.
In terms of security, GCM-SIV (AEAD) achieves usual notion of nonce-
based security of an authenticated encryption mode as long as a
unique nonce is used per authentication key per message. If,
however, the nonce is reused authenticity is still retained (unlike
in GMAC).
But there is not many implementations for GCM-SIV available except
for the one from the authors. We customized this code for
authentication only mode GMAC-SIV and run it on an x86_64, Intel(R)
Xeon(R) CPU E5-2676 v3 @ 2.40GHz with one core CPU with AES-NI
enabled. GMAC-SIV takes ~5.9 CPU cycles/byte to generate a tag of
length 16 bytes on a 48-byte NTP payload. The performance efficiency
Malhotra & Goldberg Expires April 28, 2017 [Page 9]
Internet-Draft MACs for NTP October 2016
is far less than GMAC, but is slightly better than CMAC. CMAC, on
the other hand is a standardized mode of operation and has several
open source implementations.
9. Recommendations
From the tables we clearly see that GMAC(AES) has the best latency
and throughput performance in both hardware and software
implementations. It is freely available, and there is a flexibilty
of changing the underlying block-cipher. However there are several
security problems surrounding the use of this mode, as highlighted
above, so it is not recommended.
CMAC, on the other hand, is the next best choice in terms of
performance and security. So we recommend the use of CMAC (AES).
10. Acknowledgements
The authors wish to acknowledge useful discussions with Leen
Alshenibr, Daniel Franke, Ethan Heilman, Kenny Paterson, Leonid
Reyzin, Harlan Stenn, Mayank Varia.
11. References
11.1. Normative References
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)",
RFC 4106, DOI 10.17487/RFC4106, June 2005,
<http://www.rfc-editor.org/info/rfc4106>.
[RFC4493] Song, JH., Poovendran, R., Lee, J., and T. Iwata, "The
AES-CMAC Algorithm", RFC 4493, DOI 10.17487/RFC4493, June
2006, <http://www.rfc-editor.org/info/rfc4493>.
Malhotra & Goldberg Expires April 28, 2017 [Page 10]
Internet-Draft MACs for NTP October 2016
[RFC4543] McGrew, D. and J. Viega, "The Use of Galois Message
Authentication Code (GMAC) in IPsec ESP and AH", RFC 4543,
DOI 10.17487/RFC4543, May 2006,
<http://www.rfc-editor.org/info/rfc4543>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<http://www.rfc-editor.org/info/rfc6151>.
[RFC7539] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015,
<http://www.rfc-editor.org/info/rfc7539>.
[RFC7630] Merkle, J., Ed. and M. Lochter, "HMAC-SHA-2 Authentication
Protocols in the User-based Security Model (USM) for
SNMPv3", RFC 7630, DOI 10.17487/RFC7630, October 2015,
<http://www.rfc-editor.org/info/rfc7630>.
11.2. Informative References
[BCK] Bellare, M., Canetti, R., and H. Krawczyk, "Keyed Hash
Functions and Message Authentication", in Proceedings of
Crypto'96, 1996.
[DJB] Bernstein, D., "The Poly1305-AES message-authentication
code", in Fast Software Encryption, 2005.
[GK] Gueron, S. and V. Krasnov, "The fragility of AES-GCM
authentication algorithm", in Proceedings of 11th
International Conference on Information Technology: New
Generations 2014, 2014.
[IK] Iwata, T. and K. Kurosawa, "Keyed Hash Functions and
Message Authentication", in Progress in Cryptology-
INDOCRYPT 2003, 2003.
[IOM] Iwata, T., Ohashi, K., and K. Minematsu, "Breaking and
Repairing GCM Security Proofs", in Proceedings of CRYPTO
2012, 2012.
Malhotra & Goldberg Expires April 28, 2017 [Page 11]
Internet-Draft MACs for NTP October 2016
[Joux] Joux, A., "Authentication Failures in NIST version of
GCM",
<http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/
comments/800-38_Series-Drafts/GCM/Joux_comments.pdf>.
[MB] Bellare, M., "New Proofs for NMAC and HMAC:Security
without Collision-Resistance", in Proceedings of
Crypto'96, 1996.
[NIST] Sherman, J. and J. Levine, "Usage Analysis of the NIST
Internet Time Service", in Journal of Research of the
National Institute of Standards and Technology, 2016.
[NIST-CMAC]
Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: The CMAC Mode for Authentication", in NIST
Special Publication 800-38B, 2005.
[NIST-GMAC]
Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) and GMAC", in NIST
Special Publication 800-38D, 2007.
[SIV] Gueron, S., Langley, A., and Y. Lindell,
"https://tools.ietf.org/html/draft-gueron-gcmsiv-00",
in Work in Progress, 2016.
Authors' Addresses
Aanchal Malhotra
Boston University
111 Cummington St
Boston, MA 02215
US
Email: aanchal4@bu.edu
Sharon Goldberg
Boston University
111 Cummington St
Boston, MA 02215
US
Email: goldbe@cs.bu.edu
Malhotra & Goldberg Expires April 28, 2017 [Page 12]
