Lines Matching full:packet
51 3.3. SRTP Packet Processing . . . . . . . . . . . . . . . . . 11
52 3.3.1. Packet Index Determination, and ROC, s_l Update. 13
141 SRTP can achieve high throughput and low packet expansion. SRTP
216 * limited packet expansion to support the bandwidth economy goal,
219 layers used by RTP, in particular high tolerance to packet loss
267 equivalent SRTP packet on the sending side, and intercepts SRTP
268 packets and passes an equivalent RTP packet up the stack on the
274 feedback to RTP senders, or maintain packet sequence counters. SRTCP
294 The format of an SRTP packet is illustrated in Figure 1.
321 Figure 1. The format of an SRTP packet. *Encrypted Portion is the
324 The "Encrypted Portion" of an SRTP packet consists of the encryption
326 equivalent RTP packet. The Encrypted Portion MAY be the exact size
364 particular packet. Note that the MKI SHALL NOT identify
373 data. The Authenticated Portion of an SRTP packet
375 Portion of the SRTP packet. Thus, if both encryption and
420 SRTP extracts from the RTP packet header, the ROC is maintained by
423 We define the index of the SRTP packet corresponding to a given
496 RTCP index is explicitly carried in each SRTCP packet,
525 SRTP/SRTCP parameter sharing above, separate replay lists and packet
559 port are the ones in the SRTP packet. It is assumed that, when
585 If no valid context can be found for a packet corresponding to a
586 certain context identifier, that packet MUST be discarded.
588 3.3. SRTP Packet Processing
594 construct an SRTP packet:
599 2. Determine the index of the SRTP packet using the rollover counter,
601 sequence number in the RTP packet, as described in Section 3.3.1.
613 packet (see Section 4.1, for the defined ciphers). This step uses
618 6. If the MKI indicator is set to one, append the MKI to the packet.
621 Authenticated Portion of the packet, as described in Section 4.2.
636 to the packet.
638 8. If necessary, update the ROC as in Section 3.3.1, using the packet
641 To authenticate and decrypt an SRTP packet, the receiver SHALL do the
648 packet. The algorithm uses the rollover counter and highest
650 number in the SRTP packet, as described in Section 3.3.1.
653 the context is set to one, use the MKI in the SRTP packet,
663 the packet has been replayed (Section 3.3.2), using the Replay
664 List and the index as determined in Step 2. If the packet is
665 judged to be replayed, then the packet MUST be discarded, and the
672 FAILURE" (see Section 4.2), the packet MUST be discarded from
675 6. Decrypt the Encrypted Portion of the packet (see Section 4.1, for
692 the cryptographic context as in Section 3.3.1, using the packet
697 the packet.
699 3.3.1. Packet Index Determination, and ROC, s_l Update
701 SRTP implementations use an "implicit" packet index for sequencing,
702 i.e., not all of the index is explicitly carried in the SRTP packet.
711 (see security aspects below). The sender's packet index is then
717 determine the correct index of a packet, which is the location of the
718 packet in the sequence of all SRTP packets. A robust approach for
728 sequence number (SEQ) of the first observed SRTP packet (unless the
748 After the packet has been processed and authenticated (when enabled
782 particular, 2^15 packets would need to be lost, or a packet would
789 (e.g., packet loss rate) and the cases when synchronization is likely
816 A packet is "replayed" when it is stored by an adversary, and then
823 protection. Packet indices which lag behind the packet index in the
829 The receiver checks the index of an incoming packet against the
834 After the packet has been authenticated (if necessary the window is
847 packet definition. The three mandatory fields MUST be appended to an
848 RTCP packet in order to form an equivalent SRTCP packet. The added
862 According to Section 6.1 of [RFC3550], there is a REQUIRED packet
904 Figure 2. An example of the format of a Secure RTCP packet,
905 consisting of an underlying RTCP compound packet with a Sender Report
906 and SDES packet.
919 The Encrypted Portion of an SRTCP packet consists of the encryption
921 packet, from the first RTCP packet, i.e., from the ninth (9) octet to
922 the end of the compound packet. The Authenticated Portion of an
923 SRTCP packet consists of the entire equivalent (eventually compound)
924 RTCP packet, the E flag, and the SRTCP index (after any encryption
930 The E-flag indicates if the current SRTCP packet is
932 the split of a compound RTCP packet into two lower-layer
934 clear. The E bit set to "1" indicates encrypted packet, and
935 "0" indicates non-encrypted packet.
938 The SRTCP index is a 31-bit counter for the SRTCP packet.
939 The index is explicitly included in each packet, in contrast
941 index MUST be set to zero before the first SRTCP packet is
943 each SRTCP packet is sent. In particular, after a re-key,
954 SRTCP uses the cryptographic context parameters and packet processing
958 explicitly signaled in the packet.
981 packet was encrypted or not.
994 packet given in this section (which includes the index). The
1005 protocol (e.g., it has a BYE packet) for RTP.
1007 Precautions must be taken so that the packet expansion in SRTCP (due
1036 longer packet intervals. The increase in the intervals will be
1071 The encryption transforms defined in SRTP map the SRTP packet index
1073 keystream segment encrypts a single RTP packet. The process of
1074 encrypting a packet consists of generating the keystream segment
1075 corresponding to the packet, and then bitwise exclusive-oring that
1076 keystream segment onto the payload of the RTP packet to produce the
1077 Encrypted Portion of the SRTP packet. In case the payload size is
1095 | Payload of RTP Packet |->(*)
1099 | Encrypted Portion of SRTP Packet|<--+
1124 may still need to be computed for packet authentication, in which
1152 sequence. Each packet is encrypted with a distinct keystream
1163 SRTP packet index i, and the SRTP session salting key k_s, as below.
1176 packet MUST be used, i SHALL be the 31-bit SRTCP index and k_e, k_s
1179 Note that the initial value, IV, is fixed for each packet and is
1185 needed to encrypt the largest possible RTP packet (except for IPv6
1188 packet that can be encrypted ensures the security of the encryption
1194 implementation MUST ensure that the combination of the SRTP packet
1358 in the RTCP compound packet. E and SRTCP index are the 1-bit and
1359 31-bit fields added to the packet.
1386 Portion of the packet (as specified in Figure 1) concatenated with
1407 The sender computes the tag of M and appends it to the packet. The
1444 packet index ---+
1462 packet and then, when r > 0, a key derivation is performed whenever
1496 determined in the cryptographic context, and index, the packet index
1510 purposes. The n-bit SRTP key (or salt) for this packet SHALL then be
1640 or default values), add steps to the packet processing, or even add
1741 that a member of the group sent the packet, but does not prevent
1751 offer this form of authentication in the pre-defined packet-integrity
1811 packet being successfully forged is only one in 2^32. Thus an
1814 single forged packet can be much larger if the application is
1903 11), but has the disadvantage of adding extra bits to each packet.
1921 the current SRTP packet, the corresponding master key can be found by
1929 each packet. This could be useful, as already noted, for some
1956 packet" and "until further notice". However, the maximum limit of
1961 inserted in the packet (and its indicator in the crypto context is
2073 significance, to be unique per RTP/RTCP stream and packet. The pre-
2074 defined SRTP transforms accomplish packet-uniqueness by including the
2075 packet index and stream-uniqueness by inclusion of the SSRC.
2148 MUST keep packet counts. However, when the session keys for related
2160 an RTCP BYE-packet should be sent and/or if the event should be
2173 Note: in most typical applications (assuming at least one RTCP packet
2192 distinctness of the packet indices.
2215 keystream (so that the encryption or decryption of one packet does
2239 As some RTP packet could contain highly predictable data, e.g., SID,
2297 single forged RTP packet is limited to the decoding of that
2298 particular packet. Under this condition, the size of the
2474 large difference in the packet rate in the respective directions may
2532 rekeying in a way that the maximum packet limit is not reached on any
2557 join and leave the session at any time, there may be packet loss and
2578 desired granularity, dependent on the packet rate. High rate re-
2595 an SRTCP packet arrives close to the re-keying time. The MKI
2860 determine the index i of an SRTP packet with sequence number SEQ. In
2886 RTP packet header : 806e5cba50681de55c621599
2888 RTP packet payload : 70736575646f72616e646f6d6e657373
