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RFC 7714

 
 
 

AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP)

Part 2 of 2, p. 21 to 48
Prev RFC Part

 


prevText      Top      ToC       Page 21 
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

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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.

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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

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   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.

Top      Up      ToC       Page 25 
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

Top      Up      ToC       Page 26 
   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

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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

Top      Up      ToC       Page 28 
   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

Top      Up      ToC       Page 29 
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

Top      Up      ToC       Page 30 
   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

Top      Up      ToC       Page 31 
   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

Top      Up      ToC       Page 32 
   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

Top      Up      ToC       Page 33 
   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

Top      Up      ToC       Page 34 
     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

Top      Up      ToC       Page 35 
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

Top      Up      ToC       Page 36 
   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

Top      Up      ToC       Page 37 
     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.

Top      Up      ToC       Page 38 
   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.

Top      Up      ToC       Page 39 
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

Top      Up      ToC       Page 40 
   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

Top      Up      ToC       Page 41 
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

Top      Up      ToC       Page 42 
     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

Top      Up      ToC       Page 43 
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

Top      Up      ToC       Page 44 
   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

Top      Up      ToC       Page 45 
     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>.

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   [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>.

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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>.

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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