| // Copyright 2011 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package twofish implements Bruce Schneier's Twofish encryption algorithm. |
| package twofish |
| |
| // Twofish is defined in http://www.schneier.com/paper-twofish-paper.pdf [TWOFISH] |
| |
| // This code is a port of the LibTom C implementation. |
| // See http://libtom.org/?page=features&newsitems=5&whatfile=crypt. |
| // LibTomCrypt is free for all purposes under the public domain. |
| // It was heavily inspired by the go blowfish package. |
| |
| import ( |
| "os" |
| "strconv" |
| ) |
| |
| // BlockSize is the constant block size of Twofish. |
| const BlockSize = 16 |
| |
| const mdsPolynomial = 0x169 // x^8 + x^6 + x^5 + x^3 + 1, see [TWOFISH] 4.2 |
| const rsPolynomial = 0x14d // x^8 + x^6 + x^3 + x^2 + 1, see [TWOFISH] 4.3 |
| |
| // A Cipher is an instance of Twofish encryption using a particular key. |
| type Cipher struct { |
| s [4][256]uint32 |
| k [40]uint32 |
| } |
| |
| type KeySizeError int |
| |
| func (k KeySizeError) String() string { |
| return "crypto/twofish: invalid key size " + strconv.Itoa(int(k)) |
| } |
| |
| // NewCipher creates and returns a Cipher. |
| // The key argument should be the Twofish key, 16, 24 or 32 bytes. |
| func NewCipher(key []byte) (*Cipher, os.Error) { |
| keylen := len(key) |
| |
| if keylen != 16 && keylen != 24 && keylen != 32 { |
| return nil, KeySizeError(keylen) |
| } |
| |
| // k is the number of 64 bit words in key |
| k := keylen / 8 |
| |
| // Create the S[..] words |
| var S [4 * 4]byte |
| for i := 0; i < k; i++ { |
| // Computes [y0 y1 y2 y3] = rs . [x0 x1 x2 x3 x4 x5 x6 x7] |
| for j, rsRow := range rs { |
| for k, rsVal := range rsRow { |
| S[4*i+j] ^= gfMult(key[8*i+k], rsVal, rsPolynomial) |
| } |
| } |
| } |
| |
| // Calculate subkeys |
| c := new(Cipher) |
| var tmp [4]byte |
| for i := byte(0); i < 20; i++ { |
| // A = h(p * 2x, Me) |
| for j := range tmp { |
| tmp[j] = 2 * i |
| } |
| A := h(tmp[:], key, 0) |
| |
| // B = rolc(h(p * (2x + 1), Mo), 8) |
| for j := range tmp { |
| tmp[j] = 2*i + 1 |
| } |
| B := h(tmp[:], key, 1) |
| B = rol(B, 8) |
| |
| c.k[2*i] = A + B |
| |
| // K[2i+1] = (A + 2B) <<< 9 |
| c.k[2*i+1] = rol(2*B+A, 9) |
| } |
| |
| // Calculate sboxes |
| switch k { |
| case 2: |
| for i := range c.s[0] { |
| c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][byte(i)]^S[0]]^S[4]], 0) |
| c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][byte(i)]^S[1]]^S[5]], 1) |
| c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][byte(i)]^S[2]]^S[6]], 2) |
| c.s[3][i] = mdsColumnMult(sbox[0][sbox[1][sbox[1][byte(i)]^S[3]]^S[7]], 3) |
| } |
| case 3: |
| for i := range c.s[0] { |
| c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][sbox[1][byte(i)]^S[0]]^S[4]]^S[8]], 0) |
| c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][sbox[1][byte(i)]^S[1]]^S[5]]^S[9]], 1) |
| c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][sbox[0][byte(i)]^S[2]]^S[6]]^S[10]], 2) |
| c.s[3][i] = mdsColumnMult(sbox[0][sbox[1][sbox[1][sbox[0][byte(i)]^S[3]]^S[7]]^S[11]], 3) |
| } |
| default: |
| for i := range c.s[0] { |
| c.s[0][i] = mdsColumnMult(sbox[1][sbox[0][sbox[0][sbox[1][sbox[1][byte(i)]^S[0]]^S[4]]^S[8]]^S[12]], 0) |
| c.s[1][i] = mdsColumnMult(sbox[0][sbox[0][sbox[1][sbox[1][sbox[0][byte(i)]^S[1]]^S[5]]^S[9]]^S[13]], 1) |
| c.s[2][i] = mdsColumnMult(sbox[1][sbox[1][sbox[0][sbox[0][sbox[0][byte(i)]^S[2]]^S[6]]^S[10]]^S[14]], 2) |
| c.s[3][i] = mdsColumnMult(sbox[0][sbox[1][sbox[1][sbox[0][sbox[1][byte(i)]^S[3]]^S[7]]^S[11]]^S[15]], 3) |
| } |
| } |
| |
| return c, nil |
| } |
| |
| // Reset zeros the key data, so that it will no longer appear in the process's |
| // memory. |
| func (c *Cipher) Reset() { |
| for i := range c.k { |
| c.k[i] = 0 |
| } |
| for i := range c.s { |
| for j := 0; j < 256; j++ { |
| c.s[i][j] = 0 |
| } |
| } |
| } |
| |
| // BlockSize returns the Twofish block size, 16 bytes. |
| func (c *Cipher) BlockSize() int { return BlockSize } |
| |
| // store32l stores src in dst in little-endian form. |
| func store32l(dst []byte, src uint32) { |
| dst[0] = byte(src) |
| dst[1] = byte(src >> 8) |
| dst[2] = byte(src >> 16) |
| dst[3] = byte(src >> 24) |
| return |
| } |
| |
| // load32l reads a little-endian uint32 from src. |
| func load32l(src []byte) uint32 { |
| return uint32(src[0]) | uint32(src[1])<<8 | uint32(src[2])<<16 | uint32(src[3])<<24 |
| } |
| |
| // rol returns x after a left circular rotation of y bits. |
| func rol(x, y uint32) uint32 { |
| return (x << (y & 31)) | (x >> (32 - (y & 31))) |
| } |
| |
| // ror returns x after a right circular rotation of y bits. |
| func ror(x, y uint32) uint32 { |
| return (x >> (y & 31)) | (x << (32 - (y & 31))) |
| } |
| |
| // The RS matrix. See [TWOFISH] 4.3 |
| var rs = [4][8]byte{ |
| {0x01, 0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E}, |
| {0xA4, 0x56, 0x82, 0xF3, 0x1E, 0xC6, 0x68, 0xE5}, |
| {0x02, 0xA1, 0xFC, 0xC1, 0x47, 0xAE, 0x3D, 0x19}, |
| {0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E, 0x03}, |
| } |
| |
| // sbox tables |
| var sbox = [2][256]byte{ |
| { |
| 0xa9, 0x67, 0xb3, 0xe8, 0x04, 0xfd, 0xa3, 0x76, 0x9a, 0x92, 0x80, 0x78, 0xe4, 0xdd, 0xd1, 0x38, |
| 0x0d, 0xc6, 0x35, 0x98, 0x18, 0xf7, 0xec, 0x6c, 0x43, 0x75, 0x37, 0x26, 0xfa, 0x13, 0x94, 0x48, |
| 0xf2, 0xd0, 0x8b, 0x30, 0x84, 0x54, 0xdf, 0x23, 0x19, 0x5b, 0x3d, 0x59, 0xf3, 0xae, 0xa2, 0x82, |
| 0x63, 0x01, 0x83, 0x2e, 0xd9, 0x51, 0x9b, 0x7c, 0xa6, 0xeb, 0xa5, 0xbe, 0x16, 0x0c, 0xe3, 0x61, |
| 0xc0, 0x8c, 0x3a, 0xf5, 0x73, 0x2c, 0x25, 0x0b, 0xbb, 0x4e, 0x89, 0x6b, 0x53, 0x6a, 0xb4, 0xf1, |
| 0xe1, 0xe6, 0xbd, 0x45, 0xe2, 0xf4, 0xb6, 0x66, 0xcc, 0x95, 0x03, 0x56, 0xd4, 0x1c, 0x1e, 0xd7, |
| 0xfb, 0xc3, 0x8e, 0xb5, 0xe9, 0xcf, 0xbf, 0xba, 0xea, 0x77, 0x39, 0xaf, 0x33, 0xc9, 0x62, 0x71, |
| 0x81, 0x79, 0x09, 0xad, 0x24, 0xcd, 0xf9, 0xd8, 0xe5, 0xc5, 0xb9, 0x4d, 0x44, 0x08, 0x86, 0xe7, |
| 0xa1, 0x1d, 0xaa, 0xed, 0x06, 0x70, 0xb2, 0xd2, 0x41, 0x7b, 0xa0, 0x11, 0x31, 0xc2, 0x27, 0x90, |
| 0x20, 0xf6, 0x60, 0xff, 0x96, 0x5c, 0xb1, 0xab, 0x9e, 0x9c, 0x52, 0x1b, 0x5f, 0x93, 0x0a, 0xef, |
| 0x91, 0x85, 0x49, 0xee, 0x2d, 0x4f, 0x8f, 0x3b, 0x47, 0x87, 0x6d, 0x46, 0xd6, 0x3e, 0x69, 0x64, |
| 0x2a, 0xce, 0xcb, 0x2f, 0xfc, 0x97, 0x05, 0x7a, 0xac, 0x7f, 0xd5, 0x1a, 0x4b, 0x0e, 0xa7, 0x5a, |
| 0x28, 0x14, 0x3f, 0x29, 0x88, 0x3c, 0x4c, 0x02, 0xb8, 0xda, 0xb0, 0x17, 0x55, 0x1f, 0x8a, 0x7d, |
| 0x57, 0xc7, 0x8d, 0x74, 0xb7, 0xc4, 0x9f, 0x72, 0x7e, 0x15, 0x22, 0x12, 0x58, 0x07, 0x99, 0x34, |
| 0x6e, 0x50, 0xde, 0x68, 0x65, 0xbc, 0xdb, 0xf8, 0xc8, 0xa8, 0x2b, 0x40, 0xdc, 0xfe, 0x32, 0xa4, |
| 0xca, 0x10, 0x21, 0xf0, 0xd3, 0x5d, 0x0f, 0x00, 0x6f, 0x9d, 0x36, 0x42, 0x4a, 0x5e, 0xc1, 0xe0, |
| }, |
| { |
| 0x75, 0xf3, 0xc6, 0xf4, 0xdb, 0x7b, 0xfb, 0xc8, 0x4a, 0xd3, 0xe6, 0x6b, 0x45, 0x7d, 0xe8, 0x4b, |
| 0xd6, 0x32, 0xd8, 0xfd, 0x37, 0x71, 0xf1, 0xe1, 0x30, 0x0f, 0xf8, 0x1b, 0x87, 0xfa, 0x06, 0x3f, |
| 0x5e, 0xba, 0xae, 0x5b, 0x8a, 0x00, 0xbc, 0x9d, 0x6d, 0xc1, 0xb1, 0x0e, 0x80, 0x5d, 0xd2, 0xd5, |
| 0xa0, 0x84, 0x07, 0x14, 0xb5, 0x90, 0x2c, 0xa3, 0xb2, 0x73, 0x4c, 0x54, 0x92, 0x74, 0x36, 0x51, |
| 0x38, 0xb0, 0xbd, 0x5a, 0xfc, 0x60, 0x62, 0x96, 0x6c, 0x42, 0xf7, 0x10, 0x7c, 0x28, 0x27, 0x8c, |
| 0x13, 0x95, 0x9c, 0xc7, 0x24, 0x46, 0x3b, 0x70, 0xca, 0xe3, 0x85, 0xcb, 0x11, 0xd0, 0x93, 0xb8, |
| 0xa6, 0x83, 0x20, 0xff, 0x9f, 0x77, 0xc3, 0xcc, 0x03, 0x6f, 0x08, 0xbf, 0x40, 0xe7, 0x2b, 0xe2, |
| 0x79, 0x0c, 0xaa, 0x82, 0x41, 0x3a, 0xea, 0xb9, 0xe4, 0x9a, 0xa4, 0x97, 0x7e, 0xda, 0x7a, 0x17, |
| 0x66, 0x94, 0xa1, 0x1d, 0x3d, 0xf0, 0xde, 0xb3, 0x0b, 0x72, 0xa7, 0x1c, 0xef, 0xd1, 0x53, 0x3e, |
| 0x8f, 0x33, 0x26, 0x5f, 0xec, 0x76, 0x2a, 0x49, 0x81, 0x88, 0xee, 0x21, 0xc4, 0x1a, 0xeb, 0xd9, |
| 0xc5, 0x39, 0x99, 0xcd, 0xad, 0x31, 0x8b, 0x01, 0x18, 0x23, 0xdd, 0x1f, 0x4e, 0x2d, 0xf9, 0x48, |
| 0x4f, 0xf2, 0x65, 0x8e, 0x78, 0x5c, 0x58, 0x19, 0x8d, 0xe5, 0x98, 0x57, 0x67, 0x7f, 0x05, 0x64, |
| 0xaf, 0x63, 0xb6, 0xfe, 0xf5, 0xb7, 0x3c, 0xa5, 0xce, 0xe9, 0x68, 0x44, 0xe0, 0x4d, 0x43, 0x69, |
| 0x29, 0x2e, 0xac, 0x15, 0x59, 0xa8, 0x0a, 0x9e, 0x6e, 0x47, 0xdf, 0x34, 0x35, 0x6a, 0xcf, 0xdc, |
| 0x22, 0xc9, 0xc0, 0x9b, 0x89, 0xd4, 0xed, 0xab, 0x12, 0xa2, 0x0d, 0x52, 0xbb, 0x02, 0x2f, 0xa9, |
| 0xd7, 0x61, 0x1e, 0xb4, 0x50, 0x04, 0xf6, 0xc2, 0x16, 0x25, 0x86, 0x56, 0x55, 0x09, 0xbe, 0x91, |
| }, |
| } |
| |
| // gfMult returns a·b in GF(2^8)/p |
| func gfMult(a, b byte, p uint32) byte { |
| B := [2]uint32{0, uint32(b)} |
| P := [2]uint32{0, p} |
| var result uint32 |
| |
| // branchless GF multiplier |
| for i := 0; i < 7; i++ { |
| result ^= B[a&1] |
| a >>= 1 |
| B[1] = P[B[1]>>7] ^ (B[1] << 1) |
| } |
| result ^= B[a&1] |
| return byte(result) |
| } |
| |
| // mdsColumnMult calculates y{col} where [y0 y1 y2 y3] = MDS · [x0] |
| func mdsColumnMult(in byte, col int) uint32 { |
| mul01 := in |
| mul5B := gfMult(in, 0x5B, mdsPolynomial) |
| mulEF := gfMult(in, 0xEF, mdsPolynomial) |
| |
| switch col { |
| case 0: |
| return uint32(mul01) | uint32(mul5B)<<8 | uint32(mulEF)<<16 | uint32(mulEF)<<24 |
| case 1: |
| return uint32(mulEF) | uint32(mulEF)<<8 | uint32(mul5B)<<16 | uint32(mul01)<<24 |
| case 2: |
| return uint32(mul5B) | uint32(mulEF)<<8 | uint32(mul01)<<16 | uint32(mulEF)<<24 |
| case 3: |
| return uint32(mul5B) | uint32(mul01)<<8 | uint32(mulEF)<<16 | uint32(mul5B)<<24 |
| } |
| |
| panic("unreachable") |
| } |
| |
| // h implements the S-box generation function. See [TWOFISH] 4.3.5 |
| func h(in, key []byte, offset int) uint32 { |
| var y [4]byte |
| for x := range y { |
| y[x] = in[x] |
| } |
| switch len(key) / 8 { |
| case 4: |
| y[0] = sbox[1][y[0]] ^ key[4*(6+offset)+0] |
| y[1] = sbox[0][y[1]] ^ key[4*(6+offset)+1] |
| y[2] = sbox[0][y[2]] ^ key[4*(6+offset)+2] |
| y[3] = sbox[1][y[3]] ^ key[4*(6+offset)+3] |
| fallthrough |
| case 3: |
| y[0] = sbox[1][y[0]] ^ key[4*(4+offset)+0] |
| y[1] = sbox[1][y[1]] ^ key[4*(4+offset)+1] |
| y[2] = sbox[0][y[2]] ^ key[4*(4+offset)+2] |
| y[3] = sbox[0][y[3]] ^ key[4*(4+offset)+3] |
| fallthrough |
| case 2: |
| y[0] = sbox[1][sbox[0][sbox[0][y[0]]^key[4*(2+offset)+0]]^key[4*(0+offset)+0]] |
| y[1] = sbox[0][sbox[0][sbox[1][y[1]]^key[4*(2+offset)+1]]^key[4*(0+offset)+1]] |
| y[2] = sbox[1][sbox[1][sbox[0][y[2]]^key[4*(2+offset)+2]]^key[4*(0+offset)+2]] |
| y[3] = sbox[0][sbox[1][sbox[1][y[3]]^key[4*(2+offset)+3]]^key[4*(0+offset)+3]] |
| } |
| // [y0 y1 y2 y3] = MDS . [x0 x1 x2 x3] |
| var mdsMult uint32 |
| for i := range y { |
| mdsMult ^= mdsColumnMult(y[i], i) |
| } |
| return mdsMult |
| } |
| |
| // Encrypt encrypts a 16-byte block from src to dst, which may overlap. |
| // Note that for amounts of data larger than a block, |
| // it is not safe to just call Encrypt on successive blocks; |
| // instead, use an encryption mode like CBC (see crypto/cipher/cbc.go). |
| func (c *Cipher) Encrypt(dst, src []byte) { |
| S1 := c.s[0] |
| S2 := c.s[1] |
| S3 := c.s[2] |
| S4 := c.s[3] |
| |
| // Load input |
| ia := load32l(src[0:4]) |
| ib := load32l(src[4:8]) |
| ic := load32l(src[8:12]) |
| id := load32l(src[12:16]) |
| |
| // Pre-whitening |
| ia ^= c.k[0] |
| ib ^= c.k[1] |
| ic ^= c.k[2] |
| id ^= c.k[3] |
| |
| for i := 0; i < 8; i++ { |
| k := c.k[8+i*4 : 12+i*4] |
| t2 := S2[byte(ib)] ^ S3[byte(ib>>8)] ^ S4[byte(ib>>16)] ^ S1[byte(ib>>24)] |
| t1 := S1[byte(ia)] ^ S2[byte(ia>>8)] ^ S3[byte(ia>>16)] ^ S4[byte(ia>>24)] + t2 |
| ic = ror(ic^(t1+k[0]), 1) |
| id = rol(id, 1) ^ (t2 + t1 + k[1]) |
| |
| t2 = S2[byte(id)] ^ S3[byte(id>>8)] ^ S4[byte(id>>16)] ^ S1[byte(id>>24)] |
| t1 = S1[byte(ic)] ^ S2[byte(ic>>8)] ^ S3[byte(ic>>16)] ^ S4[byte(ic>>24)] + t2 |
| ia = ror(ia^(t1+k[2]), 1) |
| ib = rol(ib, 1) ^ (t2 + t1 + k[3]) |
| } |
| |
| // Output with "undo last swap" |
| ta := ic ^ c.k[4] |
| tb := id ^ c.k[5] |
| tc := ia ^ c.k[6] |
| td := ib ^ c.k[7] |
| |
| store32l(dst[0:4], ta) |
| store32l(dst[4:8], tb) |
| store32l(dst[8:12], tc) |
| store32l(dst[12:16], td) |
| } |
| |
| // Decrypt decrypts a 16-byte block from src to dst, which may overlap. |
| func (c *Cipher) Decrypt(dst, src []byte) { |
| S1 := c.s[0] |
| S2 := c.s[1] |
| S3 := c.s[2] |
| S4 := c.s[3] |
| |
| // Load input |
| ta := load32l(src[0:4]) |
| tb := load32l(src[4:8]) |
| tc := load32l(src[8:12]) |
| td := load32l(src[12:16]) |
| |
| // Undo undo final swap |
| ia := tc ^ c.k[6] |
| ib := td ^ c.k[7] |
| ic := ta ^ c.k[4] |
| id := tb ^ c.k[5] |
| |
| for i := 8; i > 0; i-- { |
| k := c.k[4+i*4 : 8+i*4] |
| t2 := S2[byte(id)] ^ S3[byte(id>>8)] ^ S4[byte(id>>16)] ^ S1[byte(id>>24)] |
| t1 := S1[byte(ic)] ^ S2[byte(ic>>8)] ^ S3[byte(ic>>16)] ^ S4[byte(ic>>24)] + t2 |
| ia = rol(ia, 1) ^ (t1 + k[2]) |
| ib = ror(ib^(t2+t1+k[3]), 1) |
| |
| t2 = S2[byte(ib)] ^ S3[byte(ib>>8)] ^ S4[byte(ib>>16)] ^ S1[byte(ib>>24)] |
| t1 = S1[byte(ia)] ^ S2[byte(ia>>8)] ^ S3[byte(ia>>16)] ^ S4[byte(ia>>24)] + t2 |
| ic = rol(ic, 1) ^ (t1 + k[0]) |
| id = ror(id^(t2+t1+k[1]), 1) |
| } |
| |
| // Undo pre-whitening |
| ia ^= c.k[0] |
| ib ^= c.k[1] |
| ic ^= c.k[2] |
| id ^= c.k[3] |
| |
| store32l(dst[0:4], ia) |
| store32l(dst[4:8], ib) |
| store32l(dst[8:12], ic) |
| store32l(dst[12:16], id) |
| } |