参考文档
算法描述可以参照RFC1321。
在这份文档里面可以看到，基本的MD5运算函数有:
/* F, G, H and I are basic MD5 functions.
*/
#define F(x, y, z) (((x) & (y)) | (( ̃x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & ( ̃z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | ( ̃z)))
/* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
用Swift语言可以这么实现：
fileprivate func ROTATE_LEFT(_ a: UInt32, _ b: UInt32) -> UInt32 {
((a << b) | (a >> (32 - b)))
}
fileprivate func F(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
(x & y) | (~x & z)
}
fileprivate func G(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
(x & z) | (y & ~z)
}
fileprivate func H(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
x ^ y ^ z
}
fileprivate func I(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
y ^ (x | ~z)
}
MD5的转换函数描述如下:
/* MD5 basic transformation. Transforms state based on block.
*/
static void MD5Transform (state, block)
UINT4 state[4];
unsigned char block[64];
{
UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
Decode (x, block, 64);
/* Round 1 */
FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
/* Round 2 */
GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */
GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
/* Round 3 */
HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */
HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
/* Round 4 */
II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
/* Zeroize sensitive information.
MD5_memset ((POINTER)x, 0, sizeof (x));
}
MD5转换函数中有4个回合，每个回合重复地调用FF、GG、HH、II函数。FF、GG、HH、II函数的C语言描述如下。它们非常相似，唯一区别是分别使用了F、G、H、I函数。
/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \
(a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \ }
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
为了让代码更简洁，可以这些步骤参数化。MD5转换函数的Swift代码如下：
private mutating func transform() {
var m = [UInt32](repeating: 0, count: Self.blockSize)
var j = 0
for i in 0..全部代码
import Foundation
fileprivate extension UInt32 {
mutating func addSafely(_ b: UInt32) {
self = addingReportingOverflow(b).partialValue
}
}
fileprivate func ROTATE_LEFT(_ a: UInt32, _ b: UInt32) -> UInt32 {
((a << b) | (a >> (32 - b)))
}
fileprivate func F(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
(x & y) | (~x & z)
}
fileprivate func G(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
(x & z) | (y & ~z)
}
fileprivate func H(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
x ^ y ^ z
}
fileprivate func I(_ x: UInt32, _ y: UInt32, _ z: UInt32) -> UInt32 {
y ^ (x | ~z)
}
public struct MD5 {
public static let blockSize = 16
public init() {
}
public mutating func update(_ d: Data) {
for i in 0.. Data {
var buffer = [UInt8](repeating: 0, count: Self.blockSize)
var i = dataLength
data[i] = 0x80
i += 1
if dataLength < 56 {
while i < 56 {
data[i] = 0
i += 1
}
} else if dataLength >= 56 {
while i < 64 {
data[i] = 0
i += 1
}
transform()
memset(&data, 0, 56)
}
bitLength += dataLength * 8
for i in 0..<8 {
data[56 + i] = UInt8(truncatingIfNeeded: bitLength >> (8 * i))
}
transform()
var shift: UInt32 = 0
for i in 0..<4 {
shift = UInt32(8 * i)
for j in 0..<4 {
buffer[i + 4 * j] = UInt8(truncatingIfNeeded: state[j] >> shift)
}
}
return Data(buffer)
}
private mutating func transform() {
var m = [UInt32](repeating: 0, count: Self.blockSize)
var j = 0
for i in 0.. 使用方法
let data = Data(0..<100)
var md5 = MD5()
md5.update(data)
print(Array(md5.finalize()))
// [122, 206, 221, 26, 132, 164, 207, 203, 110, 122, 22, 0, 50, 66, 148, 94]