Class SrtpSession

One direction of SRTP and SRTCP with the AES_CM_128_HMAC_SHA1_80 suite, which WebRTC requires: protects outgoing packets, or checks and decrypts incoming ones.

Inheritance
object
SrtpSession
Inherited Members
Namespace: Uniform.Matrix.WebRtc.Srtp
Assembly: Uniform.Matrix.WebRtc.dll
Syntax
public sealed class SrtpSession
Remarks

Keys come from a master key and salt, as DTLS-SRTP exports them, with the key derivation rate 0. Each SSRC keeps its own rollover counter, which extends the 16-bit sequence number to the 48-bit packet index, and a 64-packet replay window. An SRTP packet is the RTP header, the payload encrypted with AES in counter mode, and an 80-bit HMAC-SHA1 tag over the header, the encrypted payload and the rollover counter. SRTCP also encrypts all after the first eight bytes, and appends the E flag and a 31-bit index before its tag.

Constructors

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SrtpSession(ReadOnlySpan<byte>, ReadOnlySpan<byte>)

Derive the session keys of one direction from its master key and salt.

Declaration
public SrtpSession(ReadOnlySpan<byte> masterKey, ReadOnlySpan<byte> masterSalt)
Parameters
Type Name Description
ReadOnlySpan<byte> masterKey
ReadOnlySpan<byte> masterSalt

Fields

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MasterKeyLength

Length of the master key.

Declaration
public const int MasterKeyLength = 16
Field Value
Type Description
int
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MasterSaltLength

Length of the master salt.

Declaration
public const int MasterSaltLength = 14
Field Value
Type Description
int
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TagLength

Length of the authentication tag.

Declaration
public const int TagLength = 10
Field Value
Type Description
int

Methods

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ProtectRtcp(ReadOnlySpan<byte>)

Return packet, a compound RTCP packet, protected: encrypted after its first eight bytes, with the E flag and index, and a tag.

Declaration
public byte[] ProtectRtcp(ReadOnlySpan<byte> packet)
Parameters
Type Name Description
ReadOnlySpan<byte> packet
Returns
Type Description
byte[]
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ProtectRtp(ReadOnlySpan<byte>)

Return packet, an RTP packet, protected: its payload encrypted and a tag appended.

Declaration
public byte[] ProtectRtp(ReadOnlySpan<byte> packet)
Parameters
Type Name Description
ReadOnlySpan<byte> packet
Returns
Type Description
byte[]
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UnprotectRtcp(ReadOnlySpan<byte>)

Return the RTCP packet in packet, an SRTCP packet, decrypted; null when its tag is wrong or it was received already.

Declaration
public byte[]? UnprotectRtcp(ReadOnlySpan<byte> packet)
Parameters
Type Name Description
ReadOnlySpan<byte> packet
Returns
Type Description
byte[]
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UnprotectRtp(ReadOnlySpan<byte>)

Return the RTP packet in packet, an SRTP packet, decrypted; null when its tag is wrong or it was received already.

Declaration
public byte[]? UnprotectRtp(ReadOnlySpan<byte> packet)
Parameters
Type Name Description
ReadOnlySpan<byte> packet
Returns
Type Description
byte[]