RFC 7714
AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP)
14. IANA Considerations
14.1. SDES
"Session Description Protocol (SDP) Security Descriptions for Media Streams" [RFC4568] defines SRTP "crypto suites". A crypto suite corresponds to a particular AEAD algorithm in SRTP. In order to allow security descriptions to signal the use of the algorithms defined in this document, IANA has registered the following crypto suites in the "SRTP Crypto Suite Registrations" subregistry of the "Session Description Protocol (SDP) Security Descriptions" registry. The ABNF [RFC5234] syntax is as follows: srtp-crypto-suite-ext = "AEAD_AES_128_GCM" / "AEAD_AES_256_GCM" / srtp-crypto-suite-ext
14.2. DTLS-SRTP
DTLS-SRTP [RFC5764] defines DTLS-SRTP "SRTP protection profiles". These profiles also correspond to the use of an AEAD algorithm in SRTP. In order to allow the use of the algorithms defined in this document in DTLS-SRTP, IANA has registered the following SRTP protection profiles: SRTP_AEAD_AES_128_GCM = {0x00, 0x07} SRTP_AEAD_AES_256_GCM = {0x00, 0x08} Below, we list the SRTP transform parameters for each of these protection profiles. Unless separate parameters for SRTP and SRTCP are explicitly listed, these parameters apply to both SRTP and SRTCP. SRTP_AEAD_AES_128_GCM cipher: AES_128_GCM cipher_key_length: 128 bits cipher_salt_length: 96 bits aead_auth_tag_length: 16 octets auth_function: NULL auth_key_length: N/A auth_tag_length: N/A maximum lifetime: at most 2^31 SRTCP packets and at most 2^48 SRTP packets SRTP_AEAD_AES_256_GCM cipher: AES_256_GCM cipher_key_length: 256 bits cipher_salt_length: 96 bits aead_auth_tag_length: 16 octets auth_function: NULL auth_key_length: N/A auth_tag_length: N/A maximum lifetime: at most 2^31 SRTCP packets and at most 2^48 SRTP packets Note that these SRTP protection profiles do not specify an auth_function, auth_key_length, or auth_tag_length, because all of these profiles use AEAD algorithms and thus do not use a separate auth_function, auth_key, or auth_tag. The term "aead_auth_tag_length" is used to emphasize that this refers to the authentication tag provided by the AEAD algorithm and that this tag is not located in the authentication tag field provided by SRTP/SRTCP.
14.3. MIKEY
In accordance with "MIKEY: Multimedia Internet KEYing" [RFC3830], IANA maintains several subregistries under "Multimedia Internet KEYing (MIKEY) Payload Name Spaces". Per this document, additions have been made to two of the MIKEY subregistries. In the "MIKEY Security Protocol Parameters" subregistry, the following has been added: Type | Meaning | Possible Values -------------------------------------------------------- 20 | AEAD authentication tag length | 16 octets This list is, of course, intended for use with GCM. It is conceivable that new AEAD algorithms introduced at some point in the future may require a different set of authentication tag lengths. In the "Encryption algorithm (Value 0)" subregistry (derived from Table 6.10.1.b of [RFC3830]), the following has been added: SRTP Encr. | Value | Default Session | Default Auth. Algorithm | | Encr. Key Length | Tag Length ----------------------------------------------------------- AES-GCM | 6 | 16 octets | 16 octets The encryption algorithm, session encryption key length, and AEAD authentication tag sizes received from MIKEY fully determine the AEAD algorithm to be used. The exact mapping is described in Section 15.15. Parameters for Use with MIKEY
MIKEY specifies the algorithm family separately from the key length (which is specified by the Session Encryption key length) and the authentication tag length (specified by the AEAD authentication tag length). +------------+-------------+-------------+ | Encryption | Encryption | AEAD Auth. | | Algorithm | Key Length | Tag Length | +============+=============+=============+ AEAD_AES_128_GCM | AES-GCM | 16 octets | 16 octets | +------------+-------------+-------------+ AEAD_AES_256_GCM | AES-GCM | 32 octets | 16 octets | +============+=============+=============+ Table 4: Mapping MIKEY Parameters to AEAD Algorithms
Section 11 of this document restricts the choice of KDF for AEAD algorithms. To enforce this restriction in MIKEY, we require that the SRTP Pseudorandom Function (PRF) has value AES-CM whenever an AEAD algorithm is used. Note that, according to Section 6.10.1 of [RFC3830], the input key length of the KDF (i.e., the SRTP master key length) is always equal to the session encryption key length. This means, for example, that AEAD_AES_256_GCM will use AES_256_CM_PRF as the KDF.16. Some RTP Test Vectors
The examples in this section are all based upon the same RTP packet 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 consisting of a 12-octet header (8040f17b 8041f8d3 5501a0b2) and a 38-octet payload (47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573), which is just the ASCII string "Gallia est omnis divisa in partes tres". The salt used (51756964 2070726f 2071756f) comes from the ASCII string "Quid pro quo". The 16-octet (128-bit) key is 00 01 02 ... 0f, and the 32-octet (256-bit) key is 00 01 02 ... 1f. At the time this document was written, the RTP payload type (1000000 binary = 64 decimal) was an unassigned value. As shown in Section 8.1, the IV is formed by XORing two 12-octet values. The first 12-octet value is formed by concatenating two zero octets, the 4-octet SSRC (found in the ninth through 12th octets of the packet), the 4-octet rollover counter (ROC) maintained at each end of the link, and the 2-octet sequence number (SEQ) (found in the third and fourth octets of the packet). The second 12-octet value is the salt, a value that is held constant at least until the key is changed. | Pad | SSRC | ROC | SEQ | 00 00 55 01 a0 b2 00 00 00 00 f1 7b salt 51 75 69 64 20 70 72 6f 20 71 75 6f ------------------------------------ IV 51 75 3c 65 80 c2 72 6f 20 71 84 14 All of the RTP examples use this IV.
16.1. SRTP AEAD_AES_128_GCM
16.1.1. SRTP AEAD_AES_128_GCM Encryption
Encrypting the following packet: 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 Form the IV | Pad | SSRC | ROC | SEQ | 00 00 55 01 a0 b2 00 00 00 00 f1 7b salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f AAD: 8040f17b 8041f8d3 5501a0b2 PT: 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 H: c6a13b37878f5b826f4f8162a1c8d879 Encrypt the Plaintext block # 0 IV||blk_cntr: 51753c6580c2726f2071841400000002 key_block: b5 2c 8f cf 92 55 fe 09 df ce a6 73 f0 10 22 b9 plain_block: 47 61 6c 6c 69 61 20 65 73 74 20 6f 6d 6e 69 73 cipher_block: f2 4d e3 a3 fb 34 de 6c ac ba 86 1c 9d 7e 4b ca block # 1 IV||blk_cntr: 51753c6580c2726f2071841400000003 key_block: 9e 07 52 a3 64 5a 2f 4f 2b cb d4 0a 30 b5 a5 fe plain_block: 20 64 69 76 69 73 61 20 69 6e 20 70 61 72 74 65 cipher_block: be 63 3b d5 0d 29 4e 6f 42 a5 f4 7a 51 c7 d1 9b block # 2 IV||blk_cntr: 51753c6580c2726f2071841400000004 key_block: 45 fe 4e ad ed 40 0a 5d 1a f3 63 f9 0c e1 49 3b plain_block: 73 20 74 72 65 73 cipher_block: 36 de 3a df 88 33 Cipher before tag appended f24de3a3 fb34de6c acba861c 9d7e4bca be633bd5 0d294e6f 42a5f47a 51c7d19b 36de3adf 8833
Compute the GMAC tag
Process the AAD
AAD word: 8040f17b8041f8d35501a0b200000000
partial hash: bcfb3d1d0e6e3e78ba45403377dba11b
Process the cipher
cipher word: f24de3a3fb34de6cacba861c9d7e4bca
partial hash: 0ebc0abe1b15b32fedd2b07888c1ef61
cipher word: be633bd50d294e6f42a5f47a51c7d19b
partial hash: 438e5797011ea860585709a2899f4685
cipher word: 36de3adf883300000000000000000000
partial hash: 336fb643310d7bac2aeaa76247f6036d
Process the length word
length word: 00000000000000600000000000000130
partial hash: 1b964067078c408c4e442a8f015e5264
Turn GHASH into GMAC
GHASH: 1b 96 40 67 07 8c 40 8c 4e 44 2a 8f 01 5e 52 64
K0: 92 0b 3f 40 b9 3d 2a 1d 1c 8b 5c d1 e5 67 5e aa
full GMAC: 89 9d 7f 27 be b1 6a 91 52 cf 76 5e e4 39 0c ce
Cipher with tag
f24de3a3 fb34de6c acba861c 9d7e4bca
be633bd5 0d294e6f 42a5f47a 51c7d19b
36de3adf 8833899d 7f27beb1 6a9152cf
765ee439 0cce
Encrypted and tagged packet:
8040f17b 8041f8d3 5501a0b2 f24de3a3
fb34de6c acba861c 9d7e4bca be633bd5
0d294e6f 42a5f47a 51c7d19b 36de3adf
8833899d 7f27beb1 6a9152cf 765ee439
0cce
16.1.2. SRTP AEAD_AES_128_GCM Decryption
Decrypting the following packet: 8040f17b 8041f8d3 5501a0b2 f24de3a3 fb34de6c acba861c 9d7e4bca be633bd5 0d294e6f 42a5f47a 51c7d19b 36de3adf 8833899d 7f27beb1 6a9152cf 765ee439 0cce Form the IV | Pad | SSRC | ROC | SEQ | 00 00 55 01 a0 b2 00 00 00 00 f1 7b salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f AAD: 8040f17b 8041f8d3 5501a0b2 CT: f24de3a3 fb34de6c acba861c 9d7e4bca be633bd5 0d294e6f 42a5f47a 51c7d19b 36de3adf 8833899d 7f27beb1 6a9152cf 765ee439 0cce IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 H: c6a13b37878f5b826f4f8162a1c8d879 Verify the received tag 89 9d 7f 27 be b1 6a 91 52 cf 76 5e e4 39 0c ce Process the AAD AAD word: 8040f17b8041f8d35501a0b200000000 partial hash: bcfb3d1d0e6e3e78ba45403377dba11b Process the cipher cipher word: f24de3a3fb34de6cacba861c9d7e4bca partial hash: 0ebc0abe1b15b32fedd2b07888c1ef61 cipher word: be633bd50d294e6f42a5f47a51c7d19b partial hash: 438e5797011ea860585709a2899f4685 cipher word: 36de3adf883300000000000000000000 partial hash: 336fb643310d7bac2aeaa76247f6036d Process the length word length word: 00000000000000600000000000000130 partial hash: 1b964067078c408c4e442a8f015e5264
Turn GHASH into GMAC
GHASH: 1b 96 40 67 07 8c 40 8c 4e 44 2a 8f 01 5e 52 64
K0: 92 0b 3f 40 b9 3d 2a 1d 1c 8b 5c d1 e5 67 5e aa
full GMAC: 89 9d 7f 27 be b1 6a 91 52 cf 76 5e e4 39 0c ce
Received tag = 899d7f27 beb16a91 52cf765e e4390cce
Computed tag = 899d7f27 beb16a91 52cf765e e4390cce
Received tag verified.
Decrypt the cipher
block # 0
IV||blk_cntr: 51753c6580c2726f2071841400000002
key_block: b5 2c 8f cf 92 55 fe 09 df ce a6 73 f0 10 22 b9
cipher_block: f2 4d e3 a3 fb 34 de 6c ac ba 86 1c 9d 7e 4b ca
plain_block: 47 61 6c 6c 69 61 20 65 73 74 20 6f 6d 6e 69 73
block # 1
IV||blk_cntr: 51753c6580c2726f2071841400000003
key_block: 9e 07 52 a3 64 5a 2f 4f 2b cb d4 0a 30 b5 a5 fe
cipher_block: be 63 3b d5 0d 29 4e 6f 42 a5 f4 7a 51 c7 d1 9b
plain_block: 20 64 69 76 69 73 61 20 69 6e 20 70 61 72 74 65
block # 2
IV||blk_cntr: 51753c6580c2726f2071841400000004
key_block: 45 fe 4e ad ed 40 0a 5d 1a f3 63 f9 0c e1 49 3b
cipher_block: 36 de 3a df 88 33
plain_block: 73 20 74 72 65 73
Verified and tagged packet:
47616c6c 69612065 7374206f 6d6e6973
20646976 69736120 696e2070 61727465
73207472 6573
16.1.3. SRTP AEAD_AES_128_GCM Authentication Tagging
Tagging the following packet: 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 Form the IV | Pad | SSRC | ROC | SEQ | 00 00 55 01 a0 b2 00 00 00 00 f1 7b salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f AAD: 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 H: c6a13b37878f5b826f4f8162a1c8d879 Compute the GMAC tag Process the AAD AAD word: 8040f17b8041f8d35501a0b247616c6c partial hash: 79f41fea34a474a77609d8925e9f2b22 AAD word: 696120657374206f6d6e697320646976 partial hash: 84093a2f85abf17ab37d3ce2f706138f AAD word: 69736120696e20706172746573207472 partial hash: ab2760fee24e6dec754739d8059cd144 AAD word: 65730000000000000000000000000000 partial hash: e84f3c55d287fc561c41d09a8aada4be Process the length word length word: 00000000000001900000000000000000 partial hash: b04200c26b81c98af55cc2eafccd1cbc Turn GHASH into GMAC GHASH: b0 42 00 c2 6b 81 c9 8a f5 5c c2 ea fc cd 1c bc K0: 92 0b 3f 40 b9 3d 2a 1d 1c 8b 5c d1 e5 67 5e aa full GMAC: 22 49 3f 82 d2 bc e3 97 e9 d7 9e 3b 19 aa 42 16 Cipher with tag 22493f82 d2bce397 e9d79e3b 19aa4216
Tagged packet:
8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
65732249 3f82d2bc e397e9d7 9e3b19aa
4216
16.1.4. SRTP AEAD_AES_128_GCM Tag Verification
Verifying the following packet:
8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
65732249 3f82d2bc e397e9d7 9e3b19aa
4216
Form the IV
| Pad | SSRC | ROC | SEQ |
00 00 55 01 a0 b2 00 00 00 00 f1 7b
salt: 51 75 69 64 20 70 72 6f 20 71 75 6f
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
AAD: 8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
6573
CT: 22493f82 d2bce397 e9d79e3b 19aa4216
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
H: c6a13b37878f5b826f4f8162a1c8d879
Verify the received tag
22 49 3f 82 d2 bc e3 97 e9 d7 9e 3b 19 aa 42 16
Process the AAD
AAD word: 8040f17b8041f8d35501a0b247616c6c
partial hash: 79f41fea34a474a77609d8925e9f2b22
AAD word: 696120657374206f6d6e697320646976
partial hash: 84093a2f85abf17ab37d3ce2f706138f
AAD word: 69736120696e20706172746573207472
partial hash: ab2760fee24e6dec754739d8059cd144
AAD word: 65730000000000000000000000000000
partial hash: e84f3c55d287fc561c41d09a8aada4be
Process the length word
length word: 00000000000001900000000000000000
partial hash: b04200c26b81c98af55cc2eafccd1cbc
Turn GHASH into GMAC
GHASH: b0 42 00 c2 6b 81 c9 8a f5 5c c2 ea fc cd 1c bc
K0: 92 0b 3f 40 b9 3d 2a 1d 1c 8b 5c d1 e5 67 5e aa
full GMAC: 22 49 3f 82 d2 bc e3 97 e9 d7 9e 3b 19 aa 42 16
Received tag = 22493f82 d2bce397 e9d79e3b 19aa4216
Computed tag = 22493f82 d2bce397 e9d79e3b 19aa4216
Received tag verified.
16.2. SRTP AEAD_AES_256_GCM
16.2.1. SRTP AEAD_AES_256_GCM Encryption
Encrypting the following packet:
8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
6573
Form the IV
| Pad | SSRC | ROC | SEQ |
00 00 55 01 a0 b2 00 00 00 00 f1 7b
salt: 51 75 69 64 20 70 72 6f 20 71 75 6f
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
AAD: 8040f17b 8041f8d3 5501a0b2
PT: 47616c6c 69612065 7374206f 6d6e6973
20646976 69736120 696e2070 61727465
73207472 6573
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
H: f29000b62a499fd0a9f39a6add2e7780
Encrypt the Plaintext
block # 0
IV||blk_cntr: 51753c6580c2726f2071841400000002
key_block: 75 d0 b2 14 c1 43 de 77 9c eb 58 95 5e 40 5a d9
plain_block: 47 61 6c 6c 69 61 20 65 73 74 20 6f 6d 6e 69 73
cipher_block: 32 b1 de 78 a8 22 fe 12 ef 9f 78 fa 33 2e 33 aa
block # 1
IV||blk_cntr: 51753c6580c2726f2071841400000003
key_block: 91 e4 7b 4e f3 2b 83 d3 dc 65 0a 72 17 8d da 6a
plain_block: 20 64 69 76 69 73 61 20 69 6e 20 70 61 72 74 65
cipher_block: b1 80 12 38 9a 58 e2 f3 b5 0b 2a 02 76 ff ae 0f
block # 2
IV||blk_cntr: 51753c6580c2726f2071841400000004
key_block: 68 86 43 eb dd 08 07 98 16 3a 16 d5 e5 04 f6 3a
plain_block: 73 20 74 72 65 73
cipher_block: 1b a6 37 99 b8 7b
Cipher before tag appended
32b1de78 a822fe12 ef9f78fa 332e33aa
b1801238 9a58e2f3 b50b2a02 76ffae0f
1ba63799 b87b
Compute the GMAC tag
Process the AAD
AAD word: 8040f17b8041f8d35501a0b200000000
partial hash: 0154dcb75485b71880e1957c877351bd
Process the cipher
cipher word: 32b1de78a822fe12ef9f78fa332e33aa
partial hash: c3f07db9a8b9cb4345eb07f793d322d2
cipher word: b18012389a58e2f3b50b2a0276ffae0f
partial hash: 6d1e66fe32eb32ecd8906ceab09db996
cipher word: 1ba63799b87b00000000000000000000
partial hash: b3d1d2f1fa3b366619bc42cd2eedafee
Process the length word
length word: 00000000000000600000000000000130
partial hash: 7debf5fa1fac3bd318d5e1a7ee401091
Turn GHASH into GMAC
GHASH: 7d eb f5 fa 1f ac 3b d3 18 d5 e1 a7 ee 40 10 91
K0: 07 48 2e cc c0 53 ed 63 e1 6e 99 df 39 e7 7c 82
full GMAC: 7a a3 db 36 df ff d6 b0 f9 bb 78 78 d7 a7 6c 13
Cipher with tag
32b1de78 a822fe12 ef9f78fa 332e33aa
b1801238 9a58e2f3 b50b2a02 76ffae0f
1ba63799 b87b7aa3 db36dfff d6b0f9bb
7878d7a7 6c13
Encrypted and tagged packet:
8040f17b 8041f8d3 5501a0b2 32b1de78
a822fe12 ef9f78fa 332e33aa b1801238
9a58e2f3 b50b2a02 76ffae0f 1ba63799
b87b7aa3 db36dfff d6b0f9bb 7878d7a7
6c13
16.2.2. SRTP AEAD_AES_256_GCM Decryption
Decrypting the following packet:
8040f17b 8041f8d3 5501a0b2 32b1de78
a822fe12 ef9f78fa 332e33aa b1801238
9a58e2f3 b50b2a02 76ffae0f 1ba63799
b87b7aa3 db36dfff d6b0f9bb 7878d7a7
6c13
Form the IV
| Pad | SSRC | ROC | SEQ |
00 00 55 01 a0 b2 00 00 00 00 f1 7b
salt: 51 75 69 64 20 70 72 6f 20 71 75 6f
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
AAD: 8040f17b 8041f8d3 5501a0b2
CT: 32b1de78 a822fe12 ef9f78fa 332e33aa
b1801238 9a58e2f3 b50b2a02 76ffae0f
1ba63799 b87b7aa3 db36dfff d6b0f9bb
7878d7a7 6c13
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
H: f29000b62a499fd0a9f39a6add2e7780
Verify the received tag
7a a3 db 36 df ff d6 b0 f9 bb 78 78 d7 a7 6c 13
Process the AAD
AAD word: 8040f17b8041f8d35501a0b200000000
partial hash: 0154dcb75485b71880e1957c877351bd
Process the cipher
cipher word: 32b1de78a822fe12ef9f78fa332e33aa
partial hash: c3f07db9a8b9cb4345eb07f793d322d2
cipher word: b18012389a58e2f3b50b2a0276ffae0f
partial hash: 6d1e66fe32eb32ecd8906ceab09db996
cipher word: 1ba63799b87b00000000000000000000
partial hash: b3d1d2f1fa3b366619bc42cd2eedafee
Process the length word
length word: 00000000000000600000000000000130
partial hash: 7debf5fa1fac3bd318d5e1a7ee401091
Turn GHASH into GMAC
GHASH: 7d eb f5 fa 1f ac 3b d3 18 d5 e1 a7 ee 40 10 91
K0: 07 48 2e cc c0 53 ed 63 e1 6e 99 df 39 e7 7c 82
full GMAC: 7a a3 db 36 df ff d6 b0 f9 bb 78 78 d7 a7 6c 13
Received tag = 7aa3db36 dfffd6b0 f9bb7878 d7a76c13
Computed tag = 7aa3db36 dfffd6b0 f9bb7878 d7a76c13
Received tag verified.
Decrypt the cipher
block # 0
IV||blk_cntr: 51753c6580c2726f2071841400000002
key_block: 75 d0 b2 14 c1 43 de 77 9c eb 58 95 5e 40 5a d9
cipher_block: 32 b1 de 78 a8 22 fe 12 ef 9f 78 fa 33 2e 33 aa
plain_block: 47 61 6c 6c 69 61 20 65 73 74 20 6f 6d 6e 69 73
block # 1
IV||blk_cntr: 51753c6580c2726f2071841400000003
key_block: 91 e4 7b 4e f3 2b 83 d3 dc 65 0a 72 17 8d da 6a
cipher_block: b1 80 12 38 9a 58 e2 f3 b5 0b 2a 02 76 ff ae 0f
plain_block: 20 64 69 76 69 73 61 20 69 6e 20 70 61 72 74 65
block # 2
IV||blk_cntr: 51753c6580c2726f2071841400000004
key_block: 68 86 43 eb dd 08 07 98 16 3a 16 d5 e5 04 f6 3a
cipher_block: 1b a6 37 99 b8 7b
plain_block: 73 20 74 72 65 73
Verified and tagged packet:
47616c6c 69612065 7374206f 6d6e6973
20646976 69736120 696e2070 61727465
73207472 6573
16.2.3. SRTP AEAD_AES_256_GCM Authentication Tagging
Tagging the following packet: 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 Form the IV | Pad | SSRC | ROC | SEQ | 00 00 55 01 a0 b2 00 00 00 00 f1 7b salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f AAD: 8040f17b 8041f8d3 5501a0b2 47616c6c 69612065 7374206f 6d6e6973 20646976 69736120 696e2070 61727465 73207472 6573 IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14 H: f29000b62a499fd0a9f39a6add2e7780 Compute the GMAC tag Process the AAD AAD word: 8040f17b8041f8d35501a0b247616c6c partial hash: c059753e6763791762ca630d8ef97714 AAD word: 696120657374206f6d6e697320646976 partial hash: a4e3401e712900dc4f1d2303bc4b2675 AAD word: 69736120696e20706172746573207472 partial hash: 1c8c1af883de0d67878f379a19c65987 AAD word: 65730000000000000000000000000000 partial hash: 958462781aa8e8feacce6d93b54472ac Process the length word length word: 00000000000001900000000000000000 partial hash: af2efb5dcfdb9900e7127721fdb56956 Turn GHASH into GMAC GHASH: af 2e fb 5d cf db 99 00 e7 12 77 21 fd b5 69 56 K0: 07 48 2e cc c0 53 ed 63 e1 6e 99 df 39 e7 7c 82 full GMAC: a8 66 d5 91 0f 88 74 63 06 7c ee fe c4 52 15 d4 Cipher with tag a866d591 0f887463 067ceefe c45215d4
Tagged packet:
8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
6573a866 d5910f88 7463067c eefec452
15d4
16.2.4. SRTP AEAD_AES_256_GCM Tag Verification
Verifying the following packet:
8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
6573a866 d5910f88 7463067c eefec452
15d4
Form the IV
| Pad | SSRC | ROC | SEQ |
00 00 55 01 a0 b2 00 00 00 00 f1 7b
salt: 51 75 69 64 20 70 72 6f 20 71 75 6f
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
AAD: 8040f17b 8041f8d3 5501a0b2 47616c6c
69612065 7374206f 6d6e6973 20646976
69736120 696e2070 61727465 73207472
6573
CT: a866d591 0f887463 067ceefe c45215d4
IV: 51 75 3c 65 80 c2 72 6f 20 71 84 14
H: f29000b62a499fd0a9f39a6add2e7780
Verify the received tag
a8 66 d5 91 0f 88 74 63 06 7c ee fe c4 52 15 d4
Process the AAD
AAD word: 8040f17b8041f8d35501a0b247616c6c
partial hash: c059753e6763791762ca630d8ef97714
AAD word: 696120657374206f6d6e697320646976
partial hash: a4e3401e712900dc4f1d2303bc4b2675
AAD word: 69736120696e20706172746573207472
partial hash: 1c8c1af883de0d67878f379a19c65987
AAD word: 65730000000000000000000000000000
partial hash: 958462781aa8e8feacce6d93b54472ac
Process the length word
length word: 00000000000001900000000000000000
partial hash: af2efb5dcfdb9900e7127721fdb56956
Turn GHASH into GMAC
GHASH: af 2e fb 5d cf db 99 00 e7 12 77 21 fd b5 69 56
K0: 07 48 2e cc c0 53 ed 63 e1 6e 99 df 39 e7 7c 82
full GMAC: a8 66 d5 91 0f 88 74 63 06 7c ee fe c4 52 15 d4
Received tag = a866d591 0f887463 067ceefe c45215d4
Computed tag = a866d591 0f887463 067ceefe c45215d4
Received tag verified.
17. RTCP Test Vectors
The examples in this section are all based upon the same RTCP packet:
81c8000e 4d617273 4e545031 4e545031
52545020 0000042a 0000eb98 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef
with 32-bit SRTCP index 000005d4.
As shown in Section 9.1, the IV is formed by XORing two 12-octet
values. The first 12-octet value is formed by concatenating
two zero octets, the 4-octet SSRC (found in the fifth through
eighth octets of the RTP packet), another two padding octets, and the
31-bit SRTCP index, right-justified in a 32-bit = 4-octet field with
a single "0" bit prepended as padding. An example of SRTCP IV
formation is shown below:
| Pad | SSRC | Pad | 0+SRTCP |
00 00 4d 61 72 73 00 00 00 00 05 d4
salt 51 75 69 64 20 70 72 6f 20 71 75 6f
------------------------------------
IV 51 75 24 05 52 03 72 6f 20 71 70 bb
In an SRTCP packet, a 1-bit Encryption flag is prepended to the
31-bit SRTCP index to form a 32-bit value we shall call the
"ESRTCP word". The E-flag is one if the SRTCP packet has been
encrypted and zero if it has been tagged but not encrypted. Note
that the ESRTCP field is only present in an SRTCP packet, not in an
RTCP packet. The full ESRTCP word is part of the AAD.
When encrypting and tagging an RTCP packet (E-flag = 1), the SRTCP
packet consists of the following fields in the following order:
- The first 8 octets of the RTCP packet (part of the AAD).
- The cipher.
- The ESRTCP word (the final part of the AAD).
- Any Raw Data that might have been appended to the end of the
original RTCP packet.
Recall that AEAD treats the authentication tag as an integral part of
the cipher, and in fact the authentication tag is the last 8 or
16 octets of the cipher.
The reader is reminded that when the RTCP packet is to be tagged but
not encrypted (E-flag = 0), GCM will produce a cipher that consists
solely of the 8-octet or 16-octet authentication tag. The tagged
SRTCP consists of the following fields in the order listed below:
- All of the AAD, except for the ESRTCP word.
- The cipher (= the authentication tag).
- The ESRTCP word (the final part of the AAD).
- Any Raw Data that might have been appended to the end of the
original RTCP packet.
17.1. SRTCP AEAD_AES_128_GCM Encryption and Tagging
Encrypting the following packet: 81c8000d 4d617273 4e545031 4e545032 52545020 0000042a 0000e930 4c756e61 deadbeef deadbeef deadbeef deadbeef deadbeef Key size = 128 bits Tag size = 16 octets Form the IV | Pad | SSRC | Pad | SRTCP | 00 00 4d 61 72 73 00 00 00 00 05 d4 salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 24 05 52 03 72 6f 20 71 70 bb Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f AAD: 81c8000d 4d617273 800005d4 PT: 4e545031 4e545032 52545020 0000042a 0000e930 4c756e61 deadbeef deadbeef deadbeef deadbeef deadbeef IV: 51 75 24 05 52 03 72 6f 20 71 70 bb H: c6a13b37878f5b826f4f8162a1c8d879 Encrypt the Plaintext block # 0 IV||blk_cntr: 517524055203726f207170bb00000002 key_block: 2d bd 18 b4 92 8e e6 4e f5 73 87 46 2f 6b 7a b3 plain_block: 4e 54 50 31 4e 54 50 32 52 54 50 20 00 00 04 2a cipher_block: 63 e9 48 85 dc da b6 7c a7 27 d7 66 2f 6b 7e 99 block # 1 IV||blk_cntr: 517524055203726f207170bb00000003 key_block: 7f f5 29 c7 20 73 9d 4c 18 db 1b 1e ad a0 d1 35 plain_block: 00 00 e9 30 4c 75 6e 61 de ad be ef de ad be ef cipher_block: 7f f5 c0 f7 6c 06 f3 2d c6 76 a5 f1 73 0d 6f da block # 2 IV||blk_cntr: 517524055203726f207170bb00000004 key_block: 92 4d 25 a9 58 9d 83 02 d5 14 99 b4 e0 14 78 15 plain_block: de ad be ef de ad be ef de ad be ef cipher_block: 4c e0 9b 46 86 30 3d ed 0b b9 27 5b Cipher before tag appended 63e94885 dcdab67c a727d766 2f6b7e99 7ff5c0f7 6c06f32d c676a5f1 730d6fda 4ce09b46 86303ded 0bb9275b
Compute the GMAC tag
Process the AAD
AAD word: 81c8000d4d617273800005d400000000
partial hash: 085d6eb166c555aa62982f630430ec6e
Process the cipher
cipher word: 63e94885dcdab67ca727d7662f6b7e99
partial hash: 8c9221be93466d68bbb16fa0d42b0187
cipher word: 7ff5c0f76c06f32dc676a5f1730d6fda
partial hash: 221ebb044ec9fd0bf116d7780f198792
cipher word: 4ce09b4686303ded0bb9275b00000000
partial hash: 50f70b9ca110ab312dce212657328dae
Process the length word
length word: 00000000000000600000000000000160
partial hash: 7296107c9716534371dfc1a30c5ffeb5
Turn GHASH into GMAC
GHASH: 72 96 10 7c 97 16 53 43 71 df c1 a3 0c 5f fe b5
K0: ba dc b4 24 01 d9 1e 6c b4 74 39 d1 49 86 14 6b
full GMAC: c8 4a a4 58 96 cf 4d 2f c5 ab f8 72 45 d9 ea de
Cipher with tag
63e94885 dcdab67c a727d766 2f6b7e99
7ff5c0f7 6c06f32d c676a5f1 730d6fda
4ce09b46 86303ded 0bb9275b c84aa458
96cf4d2f c5abf872 45d9eade
Append the ESRTCP word with the E-flag set
63e94885 dcdab67c a727d766 2f6b7e99
7ff5c0f7 6c06f32d c676a5f1 730d6fda
4ce09b46 86303ded 0bb9275b c84aa458
96cf4d2f c5abf872 45d9eade 800005d4
Encrypted and tagged packet:
81c8000d 4d617273 63e94885 dcdab67c
a727d766 2f6b7e99 7ff5c0f7 6c06f32d
c676a5f1 730d6fda 4ce09b46 86303ded
0bb9275b c84aa458 96cf4d2f c5abf872
45d9eade 800005d4
17.2. SRTCP AEAD_AES_256_GCM Verification and Decryption
Key size = 256 bits Tag size = 16 octets Process the length word Decrypting the following packet: 81c8000d 4d617273 d50ae4d1 f5ce5d30 4ba297e4 7d470c28 2c3ece5d bffe0a50 a2eaa5c1 110555be 8415f658 c61de047 6f1b6fad 1d1eb30c 4446839f 57ff6f6c b26ac3be 800005d4 Key size = 256 bits Key size = 16 octets Form the IV | Pad | SSRC | Pad | SRTCP | 00 00 4d 61 72 73 00 00 00 00 05 d4 salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 24 05 52 03 72 6f 20 71 70 bb Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f AAD: 81c8000d 4d617273 800005d4 CT: d50ae4d1 f5ce5d30 4ba297e4 7d470c28 2c3ece5d bffe0a50 a2eaa5c1 110555be 8415f658 c61de047 6f1b6fad 1d1eb30c 4446839f 57ff6f6c b26ac3be IV: 51 75 24 05 52 03 72 6f 20 71 70 bb H: f29000b62a499fd0a9f39a6add2e7780 Verify the received tag 1d 1e b3 0c 44 46 83 9f 57 ff 6f 6c b2 6a c3 be Process the AAD AAD word: 81c8000d4d617273800005d400000000 partial hash: 3ae5afd36dead5280b18950400176b5b Process the cipher cipher word: d50ae4d1f5ce5d304ba297e47d470c28 partial hash: e90fab7546f6940781227227ac926ebe cipher word: 2c3ece5dbffe0a50a2eaa5c1110555be partial hash: 9b236807d8b2dab07583adce367aa88f cipher word: 8415f658c61de0476f1b6fad00000000 partial hash: e69313f423a75e3e0b7eb93321700e86
Process the length word
length word: 00000000000000600000000000000160
partial hash: 3a284af2616fdf505faf37eec39fbc8b
Turn GHASH into GMAC
GHASH: 3a 28 4a f2 61 6f df 50 5f af 37 ee c3 9f bc 8b
K0: 27 36 f9 fe 25 29 5c cf 08 50 58 82 71 f5 7f 35
full GMAC: 1d 1e b3 0c 44 46 83 9f 57 ff 6f 6c b2 6a c3 be
Received tag = 1d1eb30c 4446839f 57ff6f6c b26ac3be
Computed tag = 1d1eb30c 4446839f 57ff6f6c b26ac3be
Received tag verified.
Decrypt the cipher
block # 0
IV||blk_cntr: 517524055203726f207170bb00000002
key_block: 9b 5e b4 e0 bb 9a 0d 02 19 f6 c7 c4 7d 47 08 02
cipher_block: d5 0a e4 d1 f5 ce 5d 30 4b a2 97 e4 7d 47 0c 28
plain_block: 4e 54 50 31 4e 54 50 32 52 54 50 20 00 00 04 2a
block # 1
IV||blk_cntr: 517524055203726f207170bb00000003
key_block: 2c 3e 27 6d f3 8b 64 31 7c 47 1b 2e cf a8 eb 51
cipher_block: 2c 3e ce 5d bf fe 0a 50 a2 ea a5 c1 11 05 55 be
plain_block: 00 00 e9 30 4c 75 6e 61 de ad be ef de ad be ef
block # 2
IV||blk_cntr: 517524055203726f207170bb00000004
key_block: 5a b8 48 b7 18 b0 5e a8 b1 b6 d1 42 3b 74 39 55
cipher_block: 84 15 f6 58 c6 1d e0 47 6f 1b 6f ad
plain_block: de ad be ef de ad be ef de ad be ef
Verified and decrypted packet:
81c8000d 4d617273 4e545031 4e545032
52545020 0000042a 0000e930 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef
17.3. SRTCP AEAD_AES_128_GCM Tagging Only
Tagging the following packet: 81c8000d 4d617273 4e545031 4e545032 52545020 0000042a 0000e930 4c756e61 deadbeef deadbeef deadbeef deadbeef deadbeef Key size = 128 bits Tag size = 16 octets Form the IV | Pad | SSRC | Pad | SRTCP | 00 00 4d 61 72 73 00 00 00 00 05 d4 salt: 51 75 69 64 20 70 72 6f 20 71 75 6f IV: 51 75 24 05 52 03 72 6f 20 71 70 bb Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f AAD: 81c8000d 4d617273 4e545031 4e545032 52545020 0000042a 0000e930 4c756e61 deadbeef deadbeef deadbeef deadbeef deadbeef 000005d4 IV: 51 75 24 05 52 03 72 6f 20 71 70 bb H: c6a13b37878f5b826f4f8162a1c8d879 Compute the GMAC tag Process the AAD AAD word: 81c8000d4d6172734e5450314e545032 partial hash: f8dbbe278e06afe17fb4fb2e67f0a22e AAD word: 525450200000042a0000e9304c756e61 partial hash: 6ccd900dfd0eb292f68f8a410d0648ec AAD word: deadbeefdeadbeefdeadbeefdeadbeef partial hash: 6a14be0ea384c6b746235ba955a57ff5 AAD word: deadbeef000005d40000000000000000 partial hash: cc81f14905670a1e37f8bc81a91997cd Process the length word length word: 00000000000001c00000000000000000 partial hash: 3ec16d4c3c0e90a59e91be415bd976d8 Turn GHASH into GMAC GHASH: 3e c1 6d 4c 3c 0e 90 a5 9e 91 be 41 5b d9 76 d8 K0: ba dc b4 24 01 d9 1e 6c b4 74 39 d1 49 86 14 6b full GMAC: 84 1d d9 68 3d d7 8e c9 2a e5 87 90 12 5f 62 b3
Cipher with tag
841dd968 3dd78ec9 2ae58790 125f62b3
Tagged packet:
81c8000d 4d617273 4e545031 4e545032
52545020 0000042a 0000e930 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef 841dd968 3dd78ec9 2ae58790
125f62b3 000005d4
17.4. SRTCP AEAD_AES_256_GCM Tag Verification
Key size = 256 bits
Tag size = 16 octets
Process the length word
Verifying the following packet:
81c8000d 4d617273 4e545031 4e545032
52545020 0000042a 0000e930 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef 91db4afb feee5a97 8fab4393
ed2615fe 000005d4
Key size = 256 bits
Key size = 16 octets
Form the IV
| Pad | SSRC | Pad | SRTCP |
00 00 4d 61 72 73 00 00 00 00 05 d4
salt: 51 75 69 64 20 70 72 6f 20 71 75 6f
IV: 51 75 24 05 52 03 72 6f 20 71 70 bb
Key: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
AAD: 81c8000d 4d617273 4e545031 4e545032
52545020 0000042a 0000e930 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef 000005d4
CT: 91db4afb feee5a97 8fab4393 ed2615fe
IV: 51 75 24 05 52 03 72 6f 20 71 70 bb
H: f29000b62a499fd0a9f39a6add2e7780
Verify the received tag
91 db 4a fb fe ee 5a 97 8f ab 43 93 ed 26 15 fe
Process the AAD
AAD word: 81c8000d4d6172734e5450314e545032
partial hash: 7bc665c71676a5a5f663b3229af4b85c
AAD word: 525450200000042a0000e9304c756e61
partial hash: 34ed77752703ab7d69f44237910e3bc0
AAD word: deadbeefdeadbeefdeadbeefdeadbeef
partial hash: 74a59f1a99282344d64ab1c8a2be6cf8
AAD word: deadbeef000005d40000000000000000
partial hash: 126335c0baa7ab1b79416ceeb9f7a518
Process the length word
length word: 00000000000001c00000000000000000
partial hash: b6edb305dbc7065887fb1b119cd36acb
Turn GHASH into GMAC
GHASH: b6 ed b3 05 db c7 06 58 87 fb 1b 11 9c d3 6a cb
K0: 27 36 f9 fe 25 29 5c cf 08 50 58 82 71 f5 7f 35
full GMAC: 91 db 4a fb fe ee 5a 97 8f ab 43 93 ed 26 15 fe
Received tag = 91db4afb feee5a97 8fab4393 ed2615fe
Computed tag = 91db4afb feee5a97 8fab4393 ed2615fe
Received tag verified.
Verified packet:
81c8000d 4d617273 4e545031 4e545032
52545020 0000042a 0000e930 4c756e61
deadbeef deadbeef deadbeef deadbeef
deadbeef
18. References
18.1. Normative References
[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>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004,
<http://www.rfc-editor.org/info/rfc3711>.
[RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K. Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830, DOI 10.17487/RFC3830, August 2004, <http://www.rfc-editor.org/info/rfc3830>. [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session Description Protocol (SDP) Security Descriptions for Media Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, <http://www.rfc-editor.org/info/rfc4568>. [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, <http://www.rfc-editor.org/info/rfc5116>. [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, <http://www.rfc-editor.org/info/rfc5234>. [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP)", RFC 5764, DOI 10.17487/RFC5764, May 2010, <http://www.rfc-editor.org/info/rfc5764>. [RFC6188] McGrew, D., "The Use of AES-192 and AES-256 in Secure RTP", RFC 6188, DOI 10.17487/RFC6188, March 2011, <http://www.rfc-editor.org/info/rfc6188>. [RFC6904] Lennox, J., "Encryption of Header Extensions in the Secure Real-time Transport Protocol (SRTP)", RFC 6904, DOI 10.17487/RFC6904, April 2013, <http://www.rfc-editor.org/info/rfc6904>.
18.2. Informative References
[BN00] Bellare, M. and C. Namprempre, "Authenticated Encryption: Relations among notions and analysis of the generic composition paradigm", Proceedings of ASIACRYPT 2000, Springer-Verlag, LNCS 1976, pp. 531-545, DOI 10.1007/3-540-44448-3_41, <http://www-cse.ucsd.edu/users/mihir/papers/oem.html>. [GCM] Dworkin, M., "NIST Special Publication 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC", U.S. National Institute of Standards and Technology, November 2007, <http://csrc.nist.gov/publications/nistpubs/ 800-38D/SP-800-38D.pdf>. [R02] Rogaway, P., "Authenticated-Encryption with Associated- Data", ACM Conference on Computer and Communications Security (CCS'02), pp. 98-107, ACM Press, DOI 10.1145/586110.586125, September 2002, <http://www.cs.ucdavis.edu/~rogaway/papers/ad.html>. [RFC4771] Lehtovirta, V., Naslund, M., and K. Norrman, "Integrity Transform Carrying Roll-Over Counter for the Secure Real-time Transport Protocol (SRTP)", RFC 4771, DOI 10.17487/RFC4771, January 2007, <http://www.rfc-editor.org/info/rfc4771>.
Acknowledgements
The authors would like to thank Michael Peck, Michael Torla, Qin Wu, Magnus Westerlund, Oscar Ohllson, Woo-Hwan Kim, John Mattsson, Richard Barnes, Morris Dworkin, Stephen Farrell, and many other reviewers who provided valuable comments on earlier draft versions of this document.Authors' Addresses
David A. McGrew Cisco Systems, Inc. 510 McCarthy Blvd. Milpitas, CA 95035 United States Phone: (408) 525 8651 Email: mcgrew@cisco.com URI: http://www.mindspring.com/~dmcgrew/dam.htm Kevin M. Igoe NSA/CSS Commercial Solutions Center National Security Agency Email: mythicalkevin@yahoo.com