Package com.eatthepath.noise

Interface NoiseTransportWriter

All Known Subinterfaces:

NoiseTransport

public interface NoiseTransportWriter

A Noise transport writer encrypts Noise transport messages. In the terminology of the Noise Protocol Framework specification, a NoiseTransportWriter instance encapsulates a "cipher state" produced by "splitting" a NoiseHandshake instance.

Noise transport writer instances are stateful and are not thread-safe.

See Also:

• NoiseHandshake.toTransportWriter()
• NoiseHandshake.toTransport()

Method Summary

Modifier and Type	Method	Description
int	getCiphertextLength(int plaintextLength)	Returns the length of the ciphertext resulting from the encryption of a plaintext of the given length.
void	rekeyWriter()	Sets the encryption key used by this writer to a new pseudo-random key derived from the current key.
byte[]	writeMessage(byte[] plaintext)	Encrypts a Noise transport message, returning a byte array sized exactly to contain the resulting ciphertext.
int	writeMessage(byte[] plaintext, int plaintextOffset, int plaintextLength, byte[] ciphertext, int ciphertextOffset)	Encrypts a Noise transport message.
ByteBuffer	writeMessage(ByteBuffer plaintext)	Encrypts a Noise transport message, returning a new byte buffer sized exactly to contain the resulting ciphertext.
int	writeMessage(ByteBuffer plaintext, ByteBuffer ciphertext)	Encrypts a Noise transport message.

Method Details

getCiphertextLength

int getCiphertextLength(int plaintextLength)

Returns the length of the ciphertext resulting from the encryption of a plaintext of the given length.

Parameters:

plaintextLength - the length of a plaintext

Returns:

the length of the ciphertext resulting from the encryption of a plaintext of the given size

writeMessage

ByteBuffer writeMessage(ByteBuffer plaintext)

Encrypts a Noise transport message, returning a new byte buffer sized exactly to contain the resulting ciphertext.

All plaintext.remaining() bytes starting at plaintext.position() are processed. Upon return, the plaintext buffer's position will be equal to its limit; its limit will not have changed. The returned ciphertext buffer's position will be zero, and its limit will be equal to its capacity.

Parameters:

plaintext - the plaintext to encrypt

Returns:

a new byte buffer containing the resulting ciphertext and AEAD tag

Throws:

IllegalArgumentException - if the ciphertext for the given plaintext would be larger than the maximum allowed Noise transport message size

See Also:

• getCiphertextLength(int)

writeMessage

int writeMessage(ByteBuffer plaintext,
 ByteBuffer ciphertext)
          throws ShortBufferException

Encrypts a Noise transport message. Callers are responsible for ensuring that the given ciphertext buffer has enough remaining capacity to hold the resulting ciphertext and AEAD tag.

All plaintext.remaining() bytes starting at plaintext.position() are processed. Upon return, the plaintext buffer's position will be equal to its limit; its limit will not have changed. The ciphertext buffer's position will have advanced by n, where n is the value returned by this method; the ciphertext buffer's limit will not have changed.

Note that the ciphertext and plaintext buffers must be different, but may refer to the same underlying byte array to facilitate in-place encryption.

Parameters:

plaintext - the plaintext to encrypt

ciphertext - the buffer into which to write the resulting ciphertext and AEAD tag

Returns:

the number of bytes written into the ciphertext buffer

Throws:

IllegalArgumentException - if the ciphertext for the given plaintext would be larger than the maximum allowed Noise transport message size

ShortBufferException - if the given ciphertext buffer does not have enough remaining capacity to hold the resulting ciphertext and AEAD tag

See Also:

• getCiphertextLength(int)

writeMessage

byte[] writeMessage(byte[] plaintext)

Encrypts a Noise transport message, returning a byte array sized exactly to contain the resulting ciphertext.

Parameters:

plaintext - the plaintext to encrypt

Returns:

a new byte array containing the resulting ciphertext

Throws:

IllegalArgumentException - if the ciphertext for the given plaintext would be larger than the maximum allowed Noise transport message size

writeMessage

int writeMessage(byte[] plaintext,
 int plaintextOffset,
 int plaintextLength,
 byte[] ciphertext,
 int ciphertextOffset)
          throws ShortBufferException

Encrypts a Noise transport message. Callers are responsible for ensuring that the given ciphertext array is large enough to hold the resulting ciphertext and AEAD tag.

Note that the ciphertext and plaintext arrays may refer to the same array, allowing for in-place encryption.

Parameters:

plaintext - a byte array containing the plaintext to encrypt

plaintextOffset - the offset within plaintext where the plaintext begins

plaintextLength - the length of the plaintext within plaintext

ciphertext - a byte array into which to write the ciphertext and AEAD tag from this encryption operation

ciphertextOffset - the position within ciphertext at which to begin writing the ciphertext and AEAD tag

Returns:

the number of bytes written into the ciphertext array

Throws:

ShortBufferException - if the ciphertext array (after its offset) is too small to hold the resulting ciphertext and AEAD tag

IndexOutOfBoundsException - if the given plaintext length exceeds the length of the plaintext array after its offset

IllegalArgumentException - if the ciphertext for the given plaintext would be larger than the maximum allowed Noise transport message size

See Also:

• getCiphertextLength(int)

rekeyWriter

void rekeyWriter()

Sets the encryption key used by this writer to a new pseudo-random key derived from the current key. This operation must be coordinated with the receiving party, otherwise messages sent to the receiving party will be unintelligible and decrypting future messages will fail.