新建 md5.go 文件，代码如下：
package main
import(
"fmt"
"crypto/md5"
"encoding/hex"
)
func main(){
data := []byte("hello world")
s := fmt.Sprintf("%x", md5.Sum(data))
fmt.Println(s)
// 也可以用这种方式
h := md5.New()
h.Write(data)
s = hex.EncodeToString(h.Sum(nil))
fmt.Println(s)
}
--------
运行结果
go run md5.go
5eb63bbbe01eeed093cb22bb8f5acdc3
5eb63bbbe01eeed093cb22bb8f5acdc3**
md5 实现原理
**
1.对MD5算法简要的叙述可以为：MD5以512位分组来处理输入的信息，且每一分组又被划分为16个32位子分组，经过了一系列的处理后，算法的输出由四个32位分组组成，将这四个32位分组级联后将生成一个128位散列值。
填充：如果输入信息的长度(bit)对512求余的结果不等于448，就需要填充使得对512求余的结果等于448。填充的方法是填充一个1和n个0。填充完后，信息的长度就为N*512+448(bit)；
2.记录信息长度：用64位来存储填充前信息长度。这64位加在第一步结果的后面，这样信息长度就变为N*512+448+64=(N+1)*512位。
3.装入标准的幻数（四个整数）：标准的幻数（物理顺序）是（A=(01234567)16，B=(89ABCDEF)16，C=(FEDCBA98)16，D=(76543210)16）。如果在程序中定义应该是（A=0X67452301，B=0XEFCDAB89，C=0X98BADCFE，D=0X10325476）
4.四轮循环运算：循环的次数是分组的个数（N+1）
1.将每一512字节细分成16个小组，每个小组64位（8个字节）
2.先认识四个线性函数(&是与,|是或,^是异或)
F(X,Y,Z)=(Y ^ Z) & X) ^ Z
G(X,Y,Z)=((X ^ Y) & Z) ^ Y
H(X,Y,Z)=X ^ Y ^ Z
I(X,Y,Z)=Y ^ (X | ^Z) 完整代码
package main
import(
"fmt"
"unsafe"
)
const Size = 16
const (
chunk = 64
init0 = 0x67452301
init1 = 0xEFCDAB89
init2 = 0x98BADCFE
init3 = 0x10325476
)
// digest represents the partial evaluation of a checksum.
type digest struct {
s [4]uint32
x [chunk]byte
nx int
len uint64
}
func (d *digest) Reset() {
d.s[0] = init0
d.s[1] = init1
d.s[2] = init2
d.s[3] = init3
d.nx = 0
d.len = 0
}
func (d *digest) Write(p []byte) (nn int, err error) {
nn = len(p)
d.len += uint64(nn)
if d.nx > 0 {
n := copy(d.x[d.nx:], p)
d.nx += n
if d.nx == chunk {
blockGeneric(d, d.x[:])
d.nx = 0
}
p = p[n:]
}
if len(p) >= chunk {
n := len(p) &^ (chunk - 1)
blockGeneric(d, p[:n])
p = p[n:]
}
if len(p) > 0 {
d.nx = copy(d.x[:], p)
}
fmt.Printf("%v\n",d)
return
}
func (d *digest) checkSum() [Size]byte {
// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
len := d.len
var tmp [64]byte
tmp[0] = 0x80
if len%64 < 56 {
d.Write(tmp[0 : 56-len%64])
fmt.Printf("%v",d)
} else {
d.Write(tmp[0 : 64+56-len%64])
}
// Length in bits.
len <<= 3
for i := uint(0); i < 8; i++ {
tmp[i] = byte(len >> (8 * i))
}
d.Write(tmp[0:8])
if d.nx != 0 {
panic("d.nx != 0")
}
var digest [Size]byte
for i, s := range d.s {
digest[i*4] = byte(s)
digest[i*4+1] = byte(s >> 8)
digest[i*4+2] = byte(s >> 16)
digest[i*4+3] = byte(s >> 24)
}
return digest
}
func blockGeneric(dig *digest, p []byte) {
a := dig.s[0]
b := dig.s[1]
c := dig.s[2]
d := dig.s[3]
var X *[16]uint32
for len(p) >= chunk {
aa, bb, cc, dd := a, b, c, d
X = (*[16]uint32)(unsafe.Pointer(&p[0]))
// Round 1.
a += (((c ^ d) & b) ^ d) + X[0] + 3614090360
a = a<<7 | a>>(32-7) + b
d += (((b ^ c) & a) ^ c) + X[1] + 3905402710
d = d<<12 | d>>(32-12) + a
c += (((a ^ b) & d) ^ b) + X[2] + 606105819
c = c<<17 | c>>(32-17) + d
b += (((d ^ a) & c) ^ a) + X[3] + 3250441966
b = b<<22 | b>>(32-22) + c
a += (((c ^ d) & b) ^ d) + X[4] + 4118548399
a = a<<7 | a>>(32-7) + b
d += (((b ^ c) & a) ^ c) + X[5] + 1200080426
d = d<<12 | d>>(32-12) + a
c += (((a ^ b) & d) ^ b) + X[6] + 2821735955
c = c<<17 | c>>(32-17) + d
b += (((d ^ a) & c) ^ a) + X[7] + 4249261313
b = b<<22 | b>>(32-22) + c
a += (((c ^ d) & b) ^ d) + X[8] + 1770035416
a = a<<7 | a>>(32-7) + b
d += (((b ^ c) & a) ^ c) + X[9] + 2336552879
d = d<<12 | d>>(32-12) + a
c += (((a ^ b) & d) ^ b) + X[10] + 4294925233
c = c<<17 | c>>(32-17) + d
b += (((d ^ a) & c) ^ a) + X[11] + 2304563134
b = b<<22 | b>>(32-22) + c
a += (((c ^ d) & b) ^ d) + X[12] + 1804603682
a = a<<7 | a>>(32-7) + b
d += (((b ^ c) & a) ^ c) + X[13] + 4254626195
d = d<<12 | d>>(32-12) + a
c += (((a ^ b) & d) ^ b) + X[14] + 2792965006
c = c<<17 | c>>(32-17) + d
b += (((d ^ a) & c) ^ a) + X[15] + 1236535329
b = b<<22 | b>>(32-22) + c
// Round 2.
a += (((b ^ c) & d) ^ c) + X[(1+5*0)&15] + 4129170786
a = a<<5 | a>>(32-5) + b
d += (((a ^ b) & c) ^ b) + X[(1+5*1)&15] + 3225465664
d = d<<9 | d>>(32-9) + a
c += (((d ^ a) & b) ^ a) + X[(1+5*2)&15] + 643717713
c = c<<14 | c>>(32-14) + d
b += (((c ^ d) & a) ^ d) + X[(1+5*3)&15] + 3921069994
b = b<<20 | b>>(32-20) + c
a += (((b ^ c) & d) ^ c) + X[(1+5*4)&15] + 3593408605
a = a<<5 | a>>(32-5) + b
d += (((a ^ b) & c) ^ b) + X[(1+5*5)&15] + 38016083
d = d<<9 | d>>(32-9) + a
c += (((d ^ a) & b) ^ a) + X[(1+5*6)&15] + 3634488961
c = c<<14 | c>>(32-14) + d
b += (((c ^ d) & a) ^ d) + X[(1+5*7)&15] + 3889429448
b = b<<20 | b>>(32-20) + c
a += (((b ^ c) & d) ^ c) + X[(1+5*8)&15] + 568446438
a = a<<5 | a>>(32-5) + b
d += (((a ^ b) & c) ^ b) + X[(1+5*9)&15] + 3275163606
d = d<<9 | d>>(32-9) + a
c += (((d ^ a) & b) ^ a) + X[(1+5*10)&15] + 4107603335
c = c<<14 | c>>(32-14) + d
b += (((c ^ d) & a) ^ d) + X[(1+5*11)&15] + 1163531501
b = b<<20 | b>>(32-20) + c
a += (((b ^ c) & d) ^ c) + X[(1+5*12)&15] + 2850285829
a = a<<5 | a>>(32-5) + b
d += (((a ^ b) & c) ^ b) + X[(1+5*13)&15] + 4243563512
d = d<<9 | d>>(32-9) + a
c += (((d ^ a) & b) ^ a) + X[(1+5*14)&15] + 1735328473
c = c<<14 | c>>(32-14) + d
b += (((c ^ d) & a) ^ d) + X[(1+5*15)&15] + 2368359562
b = b<<20 | b>>(32-20) + c
// Round 3.
a += (b ^ c ^ d) + X[(5+3*0)&15] + 4294588738
a = a<<4 | a>>(32-4) + b
d += (a ^ b ^ c) + X[(5+3*1)&15] + 2272392833
d = d<<11 | d>>(32-11) + a
c += (d ^ a ^ b) + X[(5+3*2)&15] + 1839030562
c = c<<16 | c>>(32-16) + d
b += (c ^ d ^ a) + X[(5+3*3)&15] + 4259657740
b = b<<23 | b>>(32-23) + c
a += (b ^ c ^ d) + X[(5+3*4)&15] + 2763975236
a = a<<4 | a>>(32-4) + b
d += (a ^ b ^ c) + X[(5+3*5)&15] + 1272893353
d = d<<11 | d>>(32-11) + a
c += (d ^ a ^ b) + X[(5+3*6)&15] + 4139469664
c = c<<16 | c>>(32-16) + d
b += (c ^ d ^ a) + X[(5+3*7)&15] + 3200236656
b = b<<23 | b>>(32-23) + c
a += (b ^ c ^ d) + X[(5+3*8)&15] + 681279174
a = a<<4 | a>>(32-4) + b
d += (a ^ b ^ c) + X[(5+3*9)&15] + 3936430074
d = d<<11 | d>>(32-11) + a
c += (d ^ a ^ b) + X[(5+3*10)&15] + 3572445317
c = c<<16 | c>>(32-16) + d
b += (c ^ d ^ a) + X[(5+3*11)&15] + 76029189
b = b<<23 | b>>(32-23) + c
a += (b ^ c ^ d) + X[(5+3*12)&15] + 3654602809
a = a<<4 | a>>(32-4) + b
d += (a ^ b ^ c) + X[(5+3*13)&15] + 3873151461
d = d<<11 | d>>(32-11) + a
c += (d ^ a ^ b) + X[(5+3*14)&15] + 530742520
c = c<<16 | c>>(32-16) + d
b += (c ^ d ^ a) + X[(5+3*15)&15] + 3299628645
b = b<<23 | b>>(32-23) + c
// Round 4.
a += (c ^ (b | ^d)) + X[(7*0)&15] + 4096336452
a = a<<6 | a>>(32-6) + b
d += (b ^ (a | ^c)) + X[(7*1)&15] + 1126891415
d = d<<10 | d>>(32-10) + a
c += (a ^ (d | ^b)) + X[(7*2)&15] + 2878612391
c = c<<15 | c>>(32-15) + d
b += (d ^ (c | ^a)) + X[(7*3)&15] + 4237533241
b = b<<21 | b>>(32-21) + c
a += (c ^ (b | ^d)) + X[(7*4)&15] + 1700485571
a = a<<6 | a>>(32-6) + b
d += (b ^ (a | ^c)) + X[(7*5)&15] + 2399980690
d = d<<10 | d>>(32-10) + a
c += (a ^ (d | ^b)) + X[(7*6)&15] + 4293915773
c = c<<15 | c>>(32-15) + d
b += (d ^ (c | ^a)) + X[(7*7)&15] + 2240044497
b = b<<21 | b>>(32-21) + c
a += (c ^ (b | ^d)) + X[(7*8)&15] + 1873313359
a = a<<6 | a>>(32-6) + b
d += (b ^ (a | ^c)) + X[(7*9)&15] + 4264355552
d = d<<10 | d>>(32-10) + a
c += (a ^ (d | ^b)) + X[(7*10)&15] + 2734768916
c = c<<15 | c>>(32-15) + d
b += (d ^ (c | ^a)) + X[(7*11)&15] + 1309151649
b = b<<21 | b>>(32-21) + c
a += (c ^ (b | ^d)) + X[(7*12)&15] + 4149444226
a = a<<6 | a>>(32-6) + b
d += (b ^ (a | ^c)) + X[(7*13)&15] + 3174756917
d = d<<10 | d>>(32-10) + a
c += (a ^ (d | ^b)) + X[(7*14)&15] + 718787259
c = c<<15 | c>>(32-15) + d
b += (d ^ (c | ^a)) + X[(7*15)&15] + 3951481745
b = b<<21 | b>>(32-21) + c
a += aa
b += bb
c += cc
d += dd
p = p[chunk:]
}
dig.s[0] = a
dig.s[1] = b
dig.s[2] = c
dig.s[3] = d
}
func main() {
var d digest
d.Reset()
data := []byte("hello world")
d.Write(data)
hashnum := d.checkSum()
fmt.Printf("%x\n",hashnum)
}