Swift实现MD5算法

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..<Self.blockSize {
        m[i] = UInt32(data[j]) + (UInt32(data[j + 1]) << 8) + (UInt32(data[j + 2]) << 16) + (UInt32(data[j + 3]) << 24)
        j += 4
    }
    var temp = state
    let functions = [F, G, H, I]
    var value: UInt32 = 0
    for i in 0..<functions.count {
        for item in Self.rounds[i] {
            temp[item.0].addSafely(functions[i](temp[item.1], temp[item.2], temp[item.3]))
            temp[item.0].addSafely(m[item.4])
            temp[item.0].addSafely(item.6)
            value = temp[item.1]
            value.addSafely(ROTATE_LEFT(temp[item.0], item.5))
            temp[item.0] = value
        }
    }
    for i in 0..<state.count {
        state[i].addSafely(temp[i])
    }
}

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..<d.count {
            self.data[dataLength] = d[i]
            dataLength += 1
            if dataLength == data.count {
                transform()
                bitLength += 512
                dataLength = 0
            }
        }
    }
    
    public mutating func finalize() -> 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..<Self.blockSize {
            m[i] = UInt32(data[j]) + (UInt32(data[j + 1]) << 8) + (UInt32(data[j + 2]) << 16) + (UInt32(data[j + 3]) << 24)
            j += 4
        }
        var temp = state
        let functions = [F, G, H, I]
        var value: UInt32 = 0
        for i in 0..<functions.count {
            for item in Self.rounds[i] {
                temp[item.0].addSafely(functions[i](temp[item.1], temp[item.2], temp[item.3]))
                temp[item.0].addSafely(m[item.4])
                temp[item.0].addSafely(item.6)
                value = temp[item.1]
                value.addSafely(ROTATE_LEFT(temp[item.0], item.5))
                temp[item.0] = value
            }
        }
        for i in 0..<state.count {
            state[i].addSafely(temp[i])
        }
    }
    
    private var data: [UInt8] = .init(repeating: 0, count: 64)
    
    private var dataLength = 0
    
    private var bitLength = 0
    
    private var state: [UInt32] = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]
    
    private static let rounds: [[(Int, Int, Int, Int, Int, UInt32, UInt32)]] = [
        [
            (0, 1, 2, 3, 0,  7, 0xd76aa478),
            (3, 0, 1, 2, 1, 12, 0xe8c7b756),
            (2, 3, 0, 1, 2, 17, 0x242070db),
            (1, 2, 3, 0, 3, 22, 0xc1bdceee),
            (0, 1, 2, 3, 4,  7, 0xf57c0faf),
            (3, 0, 1, 2, 5, 12, 0x4787c62a),
            (2, 3, 0, 1, 6, 17, 0xa8304613),
            (1, 2, 3, 0, 7, 22, 0xfd469501),
            (0, 1, 2, 3, 8,  7, 0x698098d8),
            (3, 0, 1, 2, 9, 12, 0x8b44f7af),
            (2, 3, 0, 1, 10, 17, 0xffff5bb1),
            (1, 2, 3, 0, 11, 22, 0x895cd7be),
            (0, 1, 2, 3, 12, 7, 0x6b901122),
            (3, 0, 1, 2, 13, 12, 0xfd987193),
            (2, 3, 0, 1, 14, 17, 0xa679438e),
            (1, 2, 3, 0, 15, 22, 0x49b40821)
        ],
        [
            (0, 1, 2, 3, 1,  5,0xf61e2562),
            (3, 0, 1, 2, 6,  9,0xc040b340),
            (2, 3, 0, 1, 11,14,0x265e5a51),
            (1, 2, 3, 0, 0, 20,0xe9b6c7aa),
            (0, 1, 2, 3, 5,  5,0xd62f105d),
            (3, 0, 1, 2, 10, 9,0x02441453),
            (2, 3, 0, 1, 15,14,0xd8a1e681),
            (1, 2, 3, 0, 4, 20,0xe7d3fbc8),
            (0, 1, 2, 3, 9,  5,0x21e1cde6),
            (3, 0, 1, 2, 14, 9,0xc33707d6),
            (2, 3, 0, 1, 3, 14,0xf4d50d87),
            (1, 2, 3, 0, 8, 20,0x455a14ed),
            (0, 1, 2, 3, 13, 5,0xa9e3e905),
            (3, 0, 1, 2, 2,  9,0xfcefa3f8),
            (2, 3, 0, 1, 7, 14,0x676f02d9),
            (1, 2, 3, 0, 12,20,0x8d2a4c8a)
        ],
        [
            (0, 1, 2, 3, 5,  4,0xfffa3942),
            (3, 0, 1, 2, 8, 11,0x8771f681),
            (2, 3, 0, 1, 11,16,0x6d9d6122),
            (1, 2, 3, 0, 14,23,0xfde5380c),
            (0, 1, 2, 3, 1,  4,0xa4beea44),
            (3, 0, 1, 2, 4, 11,0x4bdecfa9),
            (2, 3, 0, 1, 7, 16,0xf6bb4b60),
            (1, 2, 3, 0, 10,23,0xbebfbc70),
            (0, 1, 2, 3, 13, 4,0x289b7ec6),
            (3, 0, 1, 2, 0, 11,0xeaa127fa),
            (2, 3, 0, 1, 3, 16,0xd4ef3085),
            (1, 2, 3, 0, 6, 23,0x04881d05),
            (0, 1, 2, 3, 9,  4,0xd9d4d039),
            (3, 0, 1, 2, 12,11,0xe6db99e5),
            (2, 3, 0, 1, 15,16,0x1fa27cf8),
            (1, 2, 3, 0, 2, 23,0xc4ac5665)
        ],
        [
            (0, 1, 2, 3, 0,  6,0xf4292244),
            (3, 0, 1, 2, 7, 10,0x432aff97),
            (2, 3, 0, 1, 14,15,0xab9423a7),
            (1, 2, 3, 0, 5, 21,0xfc93a039),
            (0, 1, 2, 3, 12, 6,0x655b59c3),
            (3, 0, 1, 2, 3, 10,0x8f0ccc92),
            (2, 3, 0, 1, 10,15,0xffeff47d),
            (1, 2, 3, 0, 1, 21,0x85845dd1),
            (0, 1, 2, 3, 8,  6,0x6fa87e4f),
            (3, 0, 1, 2, 15,10,0xfe2ce6e0),
            (2, 3, 0, 1, 6, 15,0xa3014314),
            (1, 2, 3, 0, 13,21,0x4e0811a1),
            (0, 1, 2, 3, 4,  6,0xf7537e82),
            (3, 0, 1, 2, 11,10,0xbd3af235),
            (2, 3, 0, 1, 2, 15,0x2ad7d2bb),
            (1, 2, 3, 0, 9, 21,0xeb86d391)
        ],
    ]

}

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]

最后编辑于：2021.01.07 00:04:29

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Swift实现MD5算法

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