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server/vendor/github.com/pion/srtp/v2/srtp_cipher.go

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+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package srtp
+
+import "github.com/pion/rtp"
+
+// cipher represents a implementation of one
+// of the SRTP Specific ciphers
+type srtpCipher interface {
+	// AuthTagRTPLen/AuthTagRTCPLen return auth key length of the cipher.
+	// See the note below.
+	AuthTagRTPLen() (int, error)
+	AuthTagRTCPLen() (int, error)
+	// AEADAuthTagLen returns AEAD auth key length of the cipher.
+	// See the note below.
+	AEADAuthTagLen() (int, error)
+	getRTCPIndex([]byte) uint32
+	getMKI([]byte, bool) []byte
+
+	encryptRTP([]byte, *rtp.Header, []byte, uint32) ([]byte, error)
+	encryptRTCP([]byte, []byte, uint32, uint32) ([]byte, error)
+
+	decryptRTP([]byte, []byte, *rtp.Header, int, uint32) ([]byte, error)
+	decryptRTCP([]byte, []byte, uint32, uint32) ([]byte, error)
+}
+
+/*
+NOTE: Auth tag and AEAD auth tag are placed at the different position in SRTCP
+
+In non-AEAD cipher, the authentication tag is placed *after* the ESRTCP word
+(Encrypted-flag and SRTCP index).
+
+> AES_128_CM_HMAC_SHA1_80
+> | RTCP Header | Encrypted payload |E| SRTCP Index | Auth tag |
+>                                   ^               |----------|
+>                                   |                ^
+>                                   |                authTagLen=10
+>                                   aeadAuthTagLen=0
+
+In AEAD cipher, the AEAD authentication tag is embedded in the ciphertext.
+It is *before* the ESRTCP word (Encrypted-flag and SRTCP index).
+
+> AEAD_AES_128_GCM
+> | RTCP Header | Encrypted payload | AEAD auth tag |E| SRTCP Index |
+>                                   |---------------|               ^
+>                                    ^                              authTagLen=0
+>                                    aeadAuthTagLen=16
+
+See https://tools.ietf.org/html/rfc7714 for the full specifications.
+*/