golang模拟MD5算法

MD5 算法是一个非常复杂的加密算法，模拟实现并不是一个简单的任务。不过，我们可以简单地了解一下 MD5 算法的实现原理，并尝试编写一个基本的模拟实现。

MD5 算法使用了一系列逻辑函数、常量和位运算来实现加密过程。其中，最重要的是四个逻辑函数 F、G、H 和 I，它们分别对应了四轮加密过程中的不同操作。在模拟实现中，我们可以使用类似的函数来模拟这些操作。

下面是一个简单的 MD5 算法模拟实现示例：

package main

import (
    "fmt"
)

func main() {
    str := "hello world"
    data := []byte(str)

    // 初始化状态
    a0 := uint32(0x67452301)
    b0 := uint32(0xEFCDAB89)
    c0 := uint32(0x98BADCFE)
    d0 := uint32(0x10325476)

    // 填充数据
    data = padding(data)

    // 切片处理
    chunks := chunk(data)

    // 处理每个块
    for _, chunk := range chunks {
        // 拆分成16个32位字
        words := make([]uint32, 16)
        for i := 0; i < 16; i++ {
            words[i] = uint32(chunk[i*4]) | uint32(chunk[i*4+1])<<8 | uint32(chunk[i*4+2])<<16 | uint32(chunk[i*4+3])<<24
        }

        // 保存状态
        aa := a0
        bb := b0
        cc := c0
        dd := d0

        // 第一轮加密
        aa = round1(aa, bb, cc, dd, words[0], 7, 0xD76AA478)
        dd = round1(dd, aa, bb, cc, words[1], 12, 0xE8C7B756)
        cc = round1(cc, dd, aa, bb, words[2], 17, 0x242070DB)
        bb = round1(bb, cc, dd, aa, words[3], 22, 0xC1BDCEEE)
        aa = round1(aa, bb, cc, dd, words[4], 7, 0xF57C0FAF)
        dd = round1(dd, aa, bb, cc, words[5], 12, 0x4787C62A)
        cc = round1(cc, dd, aa, bb, words[6], 17, 0xA8304613)
        bb = round1(bb, cc, dd, aa, words[7], 22, 0xFD469501)
        aa = round1(aa, bb, cc, dd, words[8], 7, 0x698098D8)
        dd = round1(dd, aa, bb, cc, words[9], 12, 0x8B44F7AF)
        cc = round1(cc, dd, aa, bb, words[10], 17, 0xFFFF5BB1)
        bb = round1(bb, cc, dd, aa, words[11], 22, 0x895CD7BE)
        aa = round1(aa, bb, cc, dd, words[12], 7, 0x6B901122)
        dd = round1(dd, aa, bb, cc, words[13], 12, 0xFD987193)
        cc = round1(cc, dd, aa, bb, words[14], 17, 0xA679438E)
        bb = round1(bb, cc, dd, aa, words[15], 22, 0x49B40821)

        // 第二轮加密
        aa = round2(aa, bb, cc, dd, words[1], 5, 0xF61E2562)
        dd = round2(dd, aa, bb, cc, words[6], 9, 0xC040B340)
        cc = round2(cc, dd, aa, bb, words[11], 14, 0x265E5A51)
        bb = round2(bb, cc, dd, aa, words[0], 20, 0xE9B6C7AA)
        aa = round2(aa, bb, cc, dd, words[5], 5, 0xD62F105D)
        dd = round2(dd, aa, bb, cc, words[10], 9, 0x02441453)
        cc = round2(cc, dd, aa, bb, words[15], 14, 0xD8A1E681)
        bb = round2(bb, cc, dd, aa, words[4], 20, 0xE7D3FBC8)
        aa = round2(aa, bb, cc, dd, words[9], 5, 0x21E1CDE6)
        dd = round2(dd, aa, bb, cc, words[14], 9, 0xC33707D6)
        cc = round2(cc, dd, aa, bb, words[3], 14, 0xF4D50D87)
        bb = round2(bb, cc, dd, aa, words[8], 20, 0x455A14ED)
        aa = round2(aa, bb, cc, dd, words[13], 5, 0xA9E3E905)
        dd = round2(dd, aa, bb, cc, words[2], 9, 0xFCEFA3F8)
        cc = round2(cc, dd, aa, bb, words[7], 14, 0x676F02D9)
        bb = round2(bb, cc, dd, aa, words[12], 20, 0x8D2A4C8A)

        // 第三轮加密
        aa = round3(aa, bb, cc, dd, words[5], 4, 0xFFFA3942)
        dd = round3(dd, aa, bb, cc, words[8], 11, 0x8771F681)
        cc = round3(cc, dd, aa, bb, words[11], 16, 0x6D9D6122)
        bb = round3(bb, cc, dd, aa, words[14], 23, 0xFDE5380C)
        aa = round3(aa, bb, cc, dd, words[1], 4, 0xA4BEEA44)
        dd = round3(dd, aa, bb, cc, words[4], 11, 0x4BDECFA9)
        cc = round3(cc, dd, aa, bb, words[7], 16, 0xF6BB4B60)
        bb = round3(bb, cc, dd, aa, words[10], 23, 0xBEBFBC70)
        aa = round3(aa, bb, cc, dd, words[13], 4, 0x289B7EC6)
        dd = round3(dd, aa, bb, cc, words[0], 11, 0xEAA127FA)
        cc = round3(cc, dd, aa, bb, words[3], 16, 0xD4EF3085)
        bb = round3(bb, cc, dd, aa, words[6], 23, 0x04881D05)
        aa = round3(aa, bb, cc, dd, words[9], 4, 0xD9D4D039)
        dd = round3(dd, aa, bb, cc, words[12], 11, 0xE6DB99E5)
        cc = round3(cc, dd, aa, bb, words[15], 16, 0x1FA27CF8)
        bb = round3(bb, cc, dd, aa, words[2], 23, 0xC4AC5665)

        // 第四轮加密
        aa = round4(aa, bb, cc, dd, words[0], 6, 0xF4292244)
        dd = round4(dd, aa, bb, cc, words[7], 10, 0x432AFF97)
        cc = round4(cc, dd, aa, bb, words[14], 15, 0xAB9423A7)
        bb = round4(bb, cc, dd, aa, words[5], 21, 0xFC93A039)
        aa = round4(aa, bb, cc, dd, words[12], 6, 0x655B59C3)
        dd = round4(dd, aa, bb, cc, words[3], 10, 0x8F0CCC92)
        cc = round4(cc, dd, aa, bb, words[10], 15, 0xFFEFF47D)
        bb = round4(bb, cc, dd, aa, words[1], 21, 0x85845DD1)
        aa = round4(aa, bb, cc, dd, words[8], 6, 0x6FA87E4F)
        dd = round4(dd, aa, bb, cc, words[15], 10, 0xFE2CE6E0)
        cc = round4(cc, dd, aa, bb, words[6], 15, 0xA3014314)
        bb = round4(bb, cc, dd, aa, words[13], 21, 0x4E0811A1)
        aa = round4(aa, bb, cc, dd, words[4], 6, 0xF7537E82)
        dd = round4(dd, aa, bb, cc, words[11], 10, 0xBD3AF235)
        cc = round4(cc, dd, aa, bb, words[2], 15, 0x2AD7D2BB)
        bb = round4(bb, cc, dd, aa, words[9], 21, 0xEB86D391)

        // 更新状态
        a0 += aa
        b0 += bb
        c0 += cc
        d0 += dd
    }

    // 输出结果
    hash := []byte{byte(a0), byte(a0 >> 8), byte(a0 >> 16), byte(a0 >> 24),
        byte(b0), byte(b0 >> 8), byte(b0 >> 16), byte(b0 >> 24),
        byte(c0), byte(c0 >> 8), byte(c0 >> 16), byte(c0 >> 24),
        byte(d0), byte(d0 >> 8), byte(d0 >> 16), byte(d0 >> 24)}
    fmt.Printf("MD5(%s)=%x\n", str, hash)
}

func padding(data []byte) []byte {
    // 填充数据
    len := len(data)
    k := 448 - ((len * 8) % 512)
    if k < 0 {
        k += 512
    }
    padding := make([]byte, k/8+64/8)
    padding[0] = 0x80
    length := uint64(len * 8)
    padding[len(padding)-8] = byte(length)
    padding[len(padding)-7] = byte(length >> 8)
    padding[len(padding)-6] = byte(length >> 16)
    padding[len(padding)-5] = byte(length >> 24)
    padding[len(padding)-4] = byte(length >> 32)
    padding[len(padding)-3] = byte(length >> 40)
    padding[len(padding)-2] = byte(length >> 48)
    padding[len(padding)-1] = byte(length >> 56)
    return append(data, padding...)
}

func chunk(data []byte) [][]byte {
    // 切片处理
    chunks := make([][]byte, len(data)/64)
    for i := 0; i < len(data)/64; i++ {
        chunks[i] = data[i*64 : i*64+64]
    }
    return chunks
}

func round1(a, b, c, d, x, s, t uint32) uint32 {
    return b + leftrotate(a+f(b, c, d)+x+t, s)
}

func round2(a, b, c, d, x, s, t uint32) uint32 {
    return b + leftrotate(a+g(b, c, d)+x+t, s)
}

func round3(a, b, c, d, x, s, t uint32) uint32 {
    return b + leftrotate(a+h(b, c, d)+x+t, s)
}

func round4(a, b, c, d, x, s, t uint32) uint32 {
    return b + leftrotate(a+i(b, c, d)+x+t, s)
}

func f(x, y, z uint32) uint32 {
    return (x & y) | (^x & z)
}

func g(x, y, z uint32) uint32 {
    return (x & z) | (y & ^z)
}

func h(x, y, z uint32) uint32 {
    return x ^ y ^ z
}

func i(x, y, z uint32) uint32 {
    return y ^ (x | ^z)
}

func leftrotate(x uint32, n uint) uint32 {
    return (x << n) | (x >> (32 - n))
}

在这个示例中，我们使用了一个名为 `padding` 的函数来对数据进行填充，使用了一个名为 `chunk` 的函数来将数据切片处理成若干个 64 字节的块。然后，我们使用四个 `round` 函数来模拟四轮加密过程，使用四个逻辑函数来模拟四轮加密过程中的不同操作。最后，我们使用 `leftrotate` 函数来实现循环左移操作。

需要注意的是，这个模拟实现只是一个简单的示例，不具备实用性。真正的 MD5 算法要比这个复杂得多，包含了更多的细节和优化，不建议自行编写。建议使用现有的加密库来实现 MD5 加密。