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package rc2
import (
"encoding/binary"
"crypto/cipher"
"errors"
)
var pitable []byte = []byte{
0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad,
}
func expandkey(ink []byte, bits uint) (outk [64]uint16) {
var kx [128]byte
t := byte(len(ink))
t8 := byte((bits+7) / 8)
tm := byte(0xff >> ((uint(t8) * 8) - bits))
copy(kx[0:], ink[0:])
for i := t; i < 128; i++ {
// L[i] = PITABLE[L[i-1] + L[i-T]];
kx[i] = pitable[kx[i-1] + kx[i-t]]
}
// L[128-T8] = PITABLE[L[128-T8] & TM];
kx[128-t8] = pitable[kx[128-t8] & tm]
for i := 127 - int(t8); i >= 0; i-- {
// L[i] = PITABLE[L[i+1] XOR L[i+T8]];
kx[i] = pitable[kx[i+1] ^ kx[byte(i)+t8]]
}
for i := 0; i < len(outk); i++ {
outk[i] = binary.LittleEndian.Uint16(kx[i * 2:])
}
return
}
func mixround(r []uint16, kx []uint16, j *uint) {
var x uint16
x = r[0] + (r[1] & (^r[3])) + (r[2] & r[3]) + kx[*j]; *j++
r[0] = (x << 1) | (x >> 15)
x = r[1] + (r[2] & (^r[0])) + (r[3] & r[0]) + kx[*j]; *j++
r[1] = (x << 2) | (x >> 14)
x = r[2] + (r[3] & (^r[1])) + (r[0] & r[1]) + kx[*j]; *j++
r[2] = (x << 3) | (x >> 13)
x = r[3] + (r[0] & (^r[2])) + (r[1] & r[2]) + kx[*j]; *j++
r[3] = (x << 5) | (x >> 11)
}
func mashround(r []uint16, kx []uint16) {
// R[i] = R[i] + K[R[i-1] & 63];
r[0] += kx[r[3] & 63]
r[1] += kx[r[0] & 63]
r[2] += kx[r[1] & 63]
r[3] += kx[r[2] & 63]
}
func encrypt(r [4]uint16, kx []uint16) [4]uint16 {
var j uint = 0
mixround(r[0:], kx, &j) // 0
mixround(r[0:], kx, &j) // 4
mixround(r[0:], kx, &j) // 8
mixround(r[0:], kx, &j) // 12
mixround(r[0:], kx, &j) // 16
mashround(r[0:], kx)
mixround(r[0:], kx, &j) // 20
mixround(r[0:], kx, &j) // 24
mixround(r[0:], kx, &j) // 28
mixround(r[0:], kx, &j) // 32
mixround(r[0:], kx, &j) // 36
mixround(r[0:], kx, &j) // 40
mashround(r[0:], kx)
mixround(r[0:], kx, &j) // 44
mixround(r[0:], kx, &j) // 48
mixround(r[0:], kx, &j) // 52
mixround(r[0:], kx, &j) // 56
mixround(r[0:], kx, &j) // 60
return r
}
func rmashround(r []uint16, kx []uint16) {
// R[i] = R[i] + K[R[i-1] & 63];
r[3] -= kx[r[2] & 63]
r[2] -= kx[r[1] & 63]
r[1] -= kx[r[0] & 63]
r[0] -= kx[r[3] & 63]
}
func rmixround(r []uint16, kx []uint16, j *uint) {
var x uint16
x = (r[3] << 11) | (r[3] >> 5)
r[3] = x - ((r[0] & (^r[2])) + (r[1] & r[2]) + kx[*j]); *j--
x = (r[2] << 13) | (r[2] >> 3)
r[2] = x - ((r[3] & (^r[1])) + (r[0] & r[1]) + kx[*j]); *j--
x = (r[1] << 14) | (r[1] >> 2)
r[1] = x - ((r[2] & (^r[0])) + (r[3] & r[0]) + kx[*j]); *j--
x = (r[0] << 15) | (r[0] >> 1)
r[0] = x - ((r[1] & (^r[3])) + (r[2] & r[3]) + kx[*j]); *j--
}
func decrypt(r [4]uint16, kx []uint16) [4]uint16 {
var j uint = 63
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmashround(r[0:], kx)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmashround(r[0:], kx)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
rmixround(r[0:], kx, &j)
return r
}
type rc2cipher struct {
xk [64]uint16
}
func (c *rc2cipher) BlockSize() int { return 8; }
func (c *rc2cipher) Decrypt(dst, src []byte) {
var block [4]uint16
block[0] = binary.LittleEndian.Uint16(src[0:])
block[1] = binary.LittleEndian.Uint16(src[2:])
block[2] = binary.LittleEndian.Uint16(src[4:])
block[3] = binary.LittleEndian.Uint16(src[6:])
block = decrypt(block, c.xk[0:])
binary.LittleEndian.PutUint16(dst[0:], block[0])
binary.LittleEndian.PutUint16(dst[2:], block[1])
binary.LittleEndian.PutUint16(dst[4:], block[2])
binary.LittleEndian.PutUint16(dst[6:], block[3])
}
func (c *rc2cipher) Encrypt(dst, src []byte) {
var block [4]uint16
block[0] = binary.LittleEndian.Uint16(src[0:])
block[1] = binary.LittleEndian.Uint16(src[2:])
block[2] = binary.LittleEndian.Uint16(src[4:])
block[3] = binary.LittleEndian.Uint16(src[6:])
block = encrypt(block, c.xk[0:])
binary.LittleEndian.PutUint16(dst[0:], block[0])
binary.LittleEndian.PutUint16(dst[2:], block[1])
binary.LittleEndian.PutUint16(dst[4:], block[2])
binary.LittleEndian.PutUint16(dst[6:], block[3])
}
func NewCipher(k []byte) (cipher.Block, error) {
if len(k) < 1 || len(k) > 128 {
return nil, errors.New("rc2: invalid key length 1 <= len(key) <= 128")
}
return &rc2cipher{ xk: expandkey(k, uint(len(k)*8)) }, nil
}
func NewCipherReducedStrength(k []byte, bits uint) (cipher.Block, error) {
if len(k) < 1 || len(k) > 128 {
return nil, errors.New("rc2: invalid key length (1 <= len(key) <= 128)")
}
if bits < 1 || bits > 1024 {
return nil, errors.New("rc2: invalid number of effective bits (1 <= bits <= 1024)")
}
return &rc2cipher{ xk: expandkey(k, bits) }, nil
}
|
