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ABNF for SDP – Session Description Protocol

|   Session Description   |   v=   |   o=   |   s=   |   i=   |   u=   |   e=   |   p=   |   c=   |   b=   |   t=  r=  z=   |   k=   |   a=   |   m=   |   SDP Addressing   |   SDP generic rules   |   "a=" SDP Attributes   |

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SDP attributes defined in
RFC 4568 – Security Descriptions for Media Streams

RFC 4568Section 9  —  see also:  IANA

|   a=crypto   |

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attribute-fields   =/
crypto-attr   =
"a=crypto:"   tag   1*WSP   crypto-suite   1*WSP   key-params   *( 1*WSP   session-param )   CRLF
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tag   =
1*9DIGIT
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crypto-suite   =
1*( ALPHA  /  DIGIT  /  "_" )
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key-params   =
key-param   *( ";"   key-param )
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key-param   =
key-method   ":"   key-info
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key-method   =
"inline"  /  key-method-ext
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key-method-ext   =
1*( ALPHA  /  DIGIT  /  "_" )
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key-info   =
1*( %x21-3A  /  %x3C-7E )
;  visible (printing) chars except semi-colon
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session-param   =
1*( VCHAR )
;  visible (printing) chars
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Grammar for SRTP transport

RFC 4568 – Section 9.2

IANA SRTP Crypto Suite Registrations

IANA Media Stream Transports

IANA SRTP Session Parameters


crypto-suite   =
key-method   =
key-info   =
session-param   =
srtp-crypto-suite   =
"AES_CM_128_HMAC_SHA1_32"  / ;  see RFC 4568
"F8_128_HMAC_SHA1_32"  / ;  see RFC 4568
"AES_CM_128_HMAC_SHA1_80"  / ;  see RFC 4568
"SEED_CTR_128_HMAC_SHA1_80"  / ;  see  RFC 5669Section 7
"SEED_128_CCM_80"  / ;  see RFC 5669
"SEED_128_GCM_96"  / ;  see RFC 5669
"AES_192_CM_HMAC_SHA1_80"  / ;  see  RFC 6188Section 5
"AES_192_CM_HMAC_SHA1_32"  / ;  see RFC 6188
"AES_256_CM_HMAC_SHA1_80"  / ;  see RFC 6188
"AES_256_CM_HMAC_SHA1_32"  / ;  see RFC 6188
"AEAD_AES_128_GCM"  / ;  see  RFC 7714Section 14.1
"AEAD_AES_256_GCM"  / ;  see RFC 7714
srtp-crypto-suite-ext
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srtp-key-method   =
"inline"
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srtp-key-info   =
key-salt   [ "|"   lifetime ]   [ "|"   mki ]
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key-salt   =
1*( base64 )
;  binary key and salt values concatenated together, and then
; base64 encoded [RFC 4648 – Section 4]

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lifetime   =
[ "2^" ]   1*( DIGIT )
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mki   =
mki-value   ":"   mki-length
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mki-value   =
1*DIGIT
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mki-length   =
1*3DIGIT
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srtp-session-param   =
kdr  /
"UNENCRYPTED_SRTP"  /
"UNENCRYPTED_SRTCP"  /
"UNAUTHENTICATED_SRTP"  /
fec-order  /
fec-key  /
wsh  /
srtp-session-extension
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kdr   =
"KDR="   1*2( DIGIT )
;  range 0..24, power of two
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fec-order   =
"FEC_ORDER="   fec-type
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fec-type   =
"FEC_SRTP="  /  "SRTP_FEC="

fec-key   =
"FEC_KEY="   key-params
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wsh   =
"WSH="   2*DIGIT
;  minimum value is 64
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base64   =
ALPHA  /  DIGIT  /  "+"  /  "/"  /  "="
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srtp-crypto-suite-ext   =
1*( ALPHA  /  DIGIT  /  "_" )
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srtp-session-extension   =
[ "-" ]   1*( VCHAR )
;  first character must not be dash ("-")
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