forked from payt0nc/fairplay-ksm
/
oaep.go
48 lines (43 loc) · 966 Bytes
/
oaep.go
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package crypto
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/sha1"
"errors"
"fmt"
)
func OAEPDecrypt(pub *rsa.PublicKey, pri *rsa.PrivateKey, cipherText []byte) ([]byte, error) {
if len(cipherText) == 0 {
return nil, errors.New("cipherText can not be empty string.")
}
buffer := bytes.Buffer{}
for _, cipherTextBlock := range grouping(cipherText, len(pub.N.Bytes())) {
plainText, err := rsa.DecryptOAEP(sha1.New(), rand.Reader, pri, cipherTextBlock, make([]byte, 0))
if err != nil {
return nil, err
}
buffer.Write(plainText)
}
return buffer.Bytes(), nil
}
func grouping(src []byte, size int) [][]byte {
var groups [][]byte
fmt.Println(size)
srcSize := len(src)
if srcSize <= size {
groups = append(groups, src)
} else {
for len(src) != 0 {
if len(src) <= size {
groups = append(groups, src)
break
} else {
v := src[:size]
groups = append(groups, v)
src = src[size:]
}
}
}
return groups
}