cipher

Documentation

Overview

Package cipher implements standard block cipher modes that can be wrapped around low-level block cipher implementations. See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html and NIST Special Publication 800-38A.

Index

• type Block
• type BlockMode
  • func NewCBCDecrypter(b Block, iv []byte) BlockMode
  • func NewCBCEncrypter(b Block, iv []byte) BlockMode
• type OCFBResyncOption
• type Stream
  • func NewCFBDecrypter(block Block, iv []byte) Stream
  • func NewCFBEncrypter(block Block, iv []byte) Stream
  • func NewCTR(block Block, iv []byte) Stream
  • func NewOCFBDecrypter(block Block, prefix []byte, resync OCFBResyncOption) Stream
  • func NewOCFBEncrypter(block Block, randData []byte, resync OCFBResyncOption) (Stream, []byte)
  • func NewOFB(b Block, iv []byte) Stream
• type StreamReader
  • func (r StreamReader) Read(dst []byte) (n int, err os.Error)
• type StreamWriter
  • func (w StreamWriter) Close() os.Error
  • func (w StreamWriter) Write(src []byte) (n int, err os.Error)

Types

type Block

type Block interface {
	// BlockSize returns the cipher's block size.
	BlockSize() int

	// Encrypt encrypts the first block in src into dst.
	// Dst and src may point at the same memory.
	Encrypt(dst, src []byte)

	// Decrypt decrypts the first block in src into dst.
	// Dst and src may point at the same memory.
	Decrypt(dst, src []byte)
}

A Block represents an implementation of block cipher using a given key. It provides the capability to encrypt or decrypt individual blocks. The mode implementations extend that capability to streams of blocks.

type BlockMode

type BlockMode interface {
	// BlockSize returns the mode's block size.
	BlockSize() int

	// CryptBlocks encrypts or decrypts a number of blocks. The length of
	// src must be a multiple of the block size. Dst and src may point to
	// the same memory.
	CryptBlocks(dst, src []byte)
}

A BlockMode represents a block cipher running in a block-based mode (CBC, ECB etc).

func NewCBCDecrypter

func NewCBCDecrypter(b Block, iv []byte) BlockMode

NewCBCDecrypter returns a BlockMode which decrypts in cipher block chaining mode, using the given Block. The length of iv must be the same as the Block's block size as must match the iv used to encrypt the data.

func NewCBCEncrypter

func NewCBCEncrypter(b Block, iv []byte) BlockMode

NewCBCEncrypter returns a BlockMode which encrypts in cipher block chaining mode, using the given Block. The length of iv must be the same as the Block's block size.

type OCFBResyncOption

type OCFBResyncOption bool

An OCFBResyncOption determines if the "resynchronization step" of OCFB is performed.

const (
	OCFBResync   OCFBResyncOption = true
	OCFBNoResync OCFBResyncOption = false
)

type Stream

type Stream interface {
	// XORKeyStream XORs each byte in the given slice with a byte from the
	// cipher's key stream. Dst and src may point to the same memory.
	XORKeyStream(dst, src []byte)
}

A Stream represents a stream cipher.

func NewCFBDecrypter

func NewCFBDecrypter(block Block, iv []byte) Stream

NewCFBDecrypter returns a Stream which decrypts with cipher feedback mode, using the given Block. The iv must be the same length as the Block's block size.

func NewCFBEncrypter

func NewCFBEncrypter(block Block, iv []byte) Stream

NewCFBEncrypter returns a Stream which encrypts with cipher feedback mode, using the given Block. The iv must be the same length as the Block's block size.

func NewCTR

func NewCTR(block Block, iv []byte) Stream

NewCTR returns a Stream which encrypts/decrypts using the given Block in counter mode. The length of iv must be the same as the Block's block size.

func NewOCFBDecrypter

func NewOCFBDecrypter(block Block, prefix []byte, resync OCFBResyncOption) Stream

NewOCFBDecrypter returns a Stream which decrypts data with OpenPGP's cipher feedback mode using the given Block. Prefix must be the first blockSize + 2 bytes of the ciphertext, where blockSize is the Block's block size. If an incorrect key is detected then nil is returned. On successful exit, blockSize+2 bytes of decrypted data are written into prefix. Resync determines if the "resynchronization step" from RFC 4880, 13.9 step 7 is performed. Different parts of OpenPGP vary on this point.

func NewOCFBEncrypter

func NewOCFBEncrypter(block Block, randData []byte, resync OCFBResyncOption) (Stream, []byte)

NewOCFBEncrypter returns a Stream which encrypts data with OpenPGP's cipher feedback mode using the given Block, and an initial amount of ciphertext. randData must be random bytes and be the same length as the Block's block size. Resync determines if the "resynchronization step" from RFC 4880, 13.9 step 7 is performed. Different parts of OpenPGP vary on this point.

func NewOFB

func NewOFB(b Block, iv []byte) Stream

NewOFB returns a Stream that encrypts or decrypts using the block cipher b in output feedback mode. The initialization vector iv's length must be equal to b's block size.

type StreamReader

type StreamReader struct {
	S Stream
	R io.Reader
}

StreamReader wraps a Stream into an io.Reader. It simply calls XORKeyStream to process each slice of data which passes through.

func (StreamReader) Read

func (r StreamReader) Read(dst []byte) (n int, err os.Error)

type StreamWriter

type StreamWriter struct {
	S   Stream
	W   io.Writer
	Err os.Error
}

StreamWriter wraps a Stream into an io.Writer. It simply calls XORKeyStream to process each slice of data which passes through. If any Write call returns short then the StreamWriter is out of sync and must be discarded.

func (StreamWriter) Close

func (w StreamWriter) Close() os.Error

func (StreamWriter) Write

func (w StreamWriter) Write(src []byte) (n int, err os.Error)