threefish

Documentation

Overview

Package threefish implements the Threefish tweakable block cipher. Threefish is designed to be the core function of the Skein hash function family. There are three versions of Threefish

• Threefish256 processes 256 bit blocks
• Threefish512 processes 512 bit blocks
• Threefish1024 processes 1024 bit blocks

Index

• Constants
• func Decrypt1024(block *[16]uint64, keys *[17]uint64, tweak *[3]uint64)
• func Decrypt256(block *[4]uint64, keys *[5]uint64, tweak *[3]uint64)
• func Decrypt512(block *[8]uint64, keys *[9]uint64, tweak *[3]uint64)
• func Encrypt1024(block *[16]uint64, keys *[17]uint64, tweak *[3]uint64)
• func Encrypt256(block *[4]uint64, keys *[5]uint64, tweak *[3]uint64)
• func Encrypt512(block *[8]uint64, keys *[9]uint64, tweak *[3]uint64)
• func IncrementTweak(tweak *[3]uint64, ctr uint64)
• func NewCipher(tweak *[TweakSize]byte, key []byte) (cipher.Block, error)
• func UBI1024(block *[16]uint64, hVal *[17]uint64, tweak *[3]uint64)
• func UBI256(block *[4]uint64, hVal *[5]uint64, tweak *[3]uint64)
• func UBI512(block *[8]uint64, hVal *[9]uint64, tweak *[3]uint64)

Constants

const (
	// The size of the tweak in bytes.
	TweakSize = 16
	// C240 is the key schedule constant
	C240 = 0x1bd11bdaa9fc1a22
	// The block size of Threefish-256 in bytes.
	BlockSize256 = 32
	// The block size of Threefish-512 in bytes.
	BlockSize512 = 64
	// The block size of Threefish-1024 in bytes.
	BlockSize1024 = 128
)

Functions

func Decrypt1024

func Decrypt1024(block *[16]uint64, keys *[17]uint64, tweak *[3]uint64)

Decrypt1024 decrypts the 16 words of block using the expanded 1024 bit key and the 128 bit tweak. The keys[16] must be keys[0] xor keys[1] xor ... keys[15] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func Decrypt256

func Decrypt256(block *[4]uint64, keys *[5]uint64, tweak *[3]uint64)

Decrypt256 decrypts the 4 words of block using the expanded 256 bit key and the 128 bit tweak. The keys[4] must be keys[0] xor keys[1] xor ... keys[3] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func Decrypt512

func Decrypt512(block *[8]uint64, keys *[9]uint64, tweak *[3]uint64)

Decrypt512 decrypts the 8 words of block using the expanded 512 bit key and the 128 bit tweak. The keys[8] must be keys[0] xor keys[1] xor ... keys[8] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func Encrypt1024

func Encrypt1024(block *[16]uint64, keys *[17]uint64, tweak *[3]uint64)

Encrypt1024 encrypts the 16 words of block using the expanded 1024 bit key and the 128 bit tweak. The keys[16] must be keys[0] xor keys[1] xor ... keys[15] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func Encrypt256

func Encrypt256(block *[4]uint64, keys *[5]uint64, tweak *[3]uint64)

Encrypt256 encrypts the 4 words of block using the expanded 256 bit key and the 128 bit tweak. The keys[4] must be keys[0] xor keys[1] xor ... keys[3] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func Encrypt512

func Encrypt512(block *[8]uint64, keys *[9]uint64, tweak *[3]uint64)

Encrypt512 encrypts the 8 words of block using the expanded 512 bit key and the 128 bit tweak. The keys[8] must be keys[0] xor keys[1] xor ... keys[8] xor C240. The tweak[2] must be tweak[0] xor tweak[1].

func IncrementTweak

func IncrementTweak(tweak *[3]uint64, ctr uint64)

Increment the tweak by the ctr argument. Skein can consume messages up to 2^96 -1 bytes.

func NewCipher

func NewCipher(tweak *[TweakSize]byte, key []byte) (cipher.Block, error)

NewCipher returns a cipher.Block implementing the Threefish cipher. The length of the key must be 32, 64 or 128 byte. The length of the tweak must be TweakSize. The returned cipher implements:

• Threefish-256 - if len(key) = 32
• Threefish-512 - if len(key) = 64
• Threefish-1024 - if len(key) = 128

func UBI1024

func UBI1024(block *[16]uint64, hVal *[17]uint64, tweak *[3]uint64)

UBI1024 does a Threefish1024 encryption of the given block using the chain values hVal and the tweak. The chain values are updated through hVal[i] = block[i] ^ Enc(block)[i]

func UBI256

func UBI256(block *[4]uint64, hVal *[5]uint64, tweak *[3]uint64)

UBI256 does a Threefish256 encryption of the given block using the chain values hVal and the tweak. The chain values are updated through hVal[i] = block[i] ^ Enc(block)[i]

func UBI512

func UBI512(block *[8]uint64, hVal *[9]uint64, tweak *[3]uint64)

UBI512 does a Threefish512 encryption of the given block using the chain values hVal and the tweak. The chain values are updated through hVal[i] = block[i] ^ Enc(block)[i]