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DES-3D解析

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import (
"bytes"
"crypto/des"
"errors"
)

// DESedeECBEncrypt ...
func DESedeECBEncrypt(origData, key []byte) ([]byte, error) {
tkey := make([]byte, 24, 24)
copy(tkey, key)
k1 := tkey[:8]
k2 := tkey[8:16]
k3 := tkey[16:]

buf1, err := encrypt(origData, k1)
if err != nil {
return nil, err
}
buf2, err := decrypt(buf1, k2)
if err != nil {
return nil, err
}
out, err := encrypt(buf2, k3)
if err != nil {
return nil, err
}
return out, nil
}

// DESedeECBDecrypt ...
func DESedeECBDecrypt(crypted, key []byte) ([]byte, error) {
tkey := make([]byte, 24, 24)
copy(tkey, key)
k1 := tkey[:8]
k2 := tkey[8:16]
k3 := tkey[16:]
buf1, err := decrypt(crypted, k3)
if err != nil {
return nil, err
}
buf2, err := encrypt(buf1, k2)
if err != nil {
return nil, err
}
out, err := decrypt(buf2, k1)
if err != nil {
return nil, err
}
return out, nil
}

func encrypt(origData, key []byte) ([]byte, error) {
if len(origData) < 1 || len(key) < 1 {
return nil, errors.New("wrong data or key")
}
block, err := des.NewCipher(key)
if err != nil {
return nil, err
}
bs := block.BlockSize()
if len(origData)%bs != 0 {
return nil, errors.New("wrong padding")
}
out := make([]byte, len(origData))
dst := out
for len(origData) > 0 {
block.Encrypt(dst, origData[:bs])
origData = origData[bs:]
dst = dst[bs:]
}
return out, nil
}

func decrypt(crypted, key []byte) ([]byte, error) {
if len(crypted) < 1 || len(key) < 1 {
return nil, errors.New("wrong data or key")
}
block, err := des.NewCipher(key)
if err != nil {
return nil, err
}
out := make([]byte, len(crypted))
dst := out
bs := block.BlockSize()
if len(crypted)%bs != 0 {
return nil, errors.New("wrong crypted size")
}

for len(crypted) > 0 {
block.Decrypt(dst, crypted[:bs])
crypted = crypted[bs:]
dst = dst[bs:]
}

return out, nil
}

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