Class AesFunctions

This class contains static fuctions for performing AES encryption and decryption operations for SRTP and SRTCP.

Inheritance

object

AesFunctions

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

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Namespace: SipLib.RtpCrypto

Assembly: SipLib.dll

Syntax

public static class AesFunctions

Methods

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AesCounterModeTransform(byte[], byte[], byte[], byte[])

Encrypts or decrypts a block of bytes using AES in Counter Mode. RFC 3711 defines the AES Counter Mode algorithm for SRTP and SRTCP.

Declaration

public static void AesCounterModeTransform(byte[] key, byte[] salt, byte[] Input, byte[] Output)

Parameters

Type	Name	Description
byte[]	key	Encryption key. The array length must be a valid length for the AES algorithm. Valid lengths are: 16 bytes (AES-128), 24 bytes (AES-192) or 32 bytes (AES-256).
byte[]	salt	Salt value to use. This must be 16 bytes (128 bits) long.
byte[]	Input	Input byte array to encrypt or decrypt.
byte[]	Output	Output encrypted or decrypted byte array. Must be the same length or longer than the Input input array.

Remarks

This function can be used to either encrypt an input array or to produce a key stream which can then be used to encrypt some data.To encrypt data, pass the data into the Input array.

To generate a key stream, pass in an array of 0s in the Input array and the Output array will contain the key stream.. Then XOR the key stream in the Output array with the data to be encrypted.

The encryption and decryption operations are symetric. To encrypt a packet, pass in the plain text as the input. To decrypt a packet, pass in the encrypted packet as the input.

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AesCounterModeTransform(byte[], byte[], byte[], int, int, byte[])

Encrypts or decrypts a block of bytes using AES in Counter Mode. RFC 3711 defines the AES Counter Mode algorithm for SRTP and SRTCP.

Declaration

public static void AesCounterModeTransform(byte[] key, byte[] salt, byte[] Input, int StartIdx, int NumInputBytes, byte[] Output)

Parameters

Type	Name	Description
byte[]	key	Encryption key. The array length must be a valid length for the AES algorithm. Valid lengths are: 16 bytes (AES-128), 24 bytes (AES-192) or 32 bytes (AES-256).
byte[]	salt	Salt value to use. This must be 16 bytes (128 bits) long.
byte[]	Input	Input byte array to encrypt or decrypt.
int	StartIdx	Starting index in the Input array.
int	NumInputBytes	Number of bytes in the input array to process.
byte[]	Output	Output encrypted or decrypted byte array. Must be the same length or longer than NumInputBytes

Remarks

This function can be used to either encrypt an input array or to produce a key stream which can then be used to encrypt some data.To encrypt data, pass the data into the Input array.

To generate a key stream, pass in an array of 0s in the Input array and the Output array will contain the key stream.. Then XOR the key stream in the Output array with the data to be encrypted.

The encryption and decryption operations are symetric. To encrypt a packet, pass in the plain text as the input. To decrypt a packet, pass in the encrypted packet as the input.

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AesF8ModeTransform(byte[], byte[], byte[], byte[], byte[])

Encrypts or Decrypts a block of bytes using the AES in F8 mode. Section 4.1.2.1 of RFC 3711 specifies the AES in F8 mode algorithm. This algorithm only supports AES-128.

Declaration

public static void AesF8ModeTransform(byte[] k_e, byte[] k_s, byte[] IV, byte[] Input, byte[] Output)

Parameters

Type	Name	Description
byte[]	k_e	Encryption key. Must be 16 bytes (128 bits) long.
byte[]	k_s	Salt value to use.
byte[]	IV	Initialization Vector (IV) to use. Must be the same length as the k_e input array.
byte[]	Input	Input byte array to encrypt or decrypt.
byte[]	Output	Output encrypted or decrypted byte array. Must be the same length or longer than the Input input array.

Remarks

This function can be used to either encrypt an input array or to produce a key stream which can then be used to encrypt some data.To encrypt data, pass the data into the Input array.

To generate a key stream, pass in an array of 0s in the Input array and the Output array will contain the key stream.. Then XOR the key stream in the Output array with the data to be encrypted.

The encryption and decryption operations are symetric. To encrypt a packet, pass in the plain text as the input. To decrypt a packet, pass in the encrypted packet as the input.

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AesF8ModeTransform(byte[], byte[], byte[], byte[], int, int, byte[])

Encrypts or Decrypts a block of bytes using the AES in F8 mode. Section 4.1.2.1 of RFC 3711 specifies the AES in F8 mode algorithm. This algorithm only supports AES-128.

Declaration

public static void AesF8ModeTransform(byte[] k_e, byte[] k_s, byte[] IV, byte[] Input, int StartIdx, int NumInputBytes, byte[] Output)

Parameters

Type	Name	Description
byte[]	k_e	Encryption key. Must be 16 bytes (128 bits) long.
byte[]	k_s	Salt value to use.
byte[]	IV	Initialization Vector (IV) to use. Must be the same length as the k_e input array.
byte[]	Input	Input byte array to encrypt or decrypt.
int	StartIdx	The index in the Input array to start processing at.
int	NumInputBytes	The number of bytes in the Input array to process.
byte[]	Output	Output encrypted or decrypted byte array. Must be the same length or longer than the Input input array.

Remarks

This function can be used to either encrypt an input array or to produce a key stream which can then be used to encrypt some data.To encrypt data, pass the data into the Input array.

To generate a key stream, pass in an array of 0s in the Input array and the Output array will contain the key stream.. Then XOR the key stream in the Output array with the data to be encrypted.

The encryption and decryption operations are symetric. To encrypt a packet, pass in the plain text as the input. To decrypt a packet, pass in the encrypted packet as the input.