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package crypto
import (
"fmt"
"math/big"
)
type RSAKeyParameters interface {
Modulus() *big.Int
Exponent() *big.Int
Private() bool
}
func NewRSAKeyParameters(isPrivate bool, modulus, exponent *big.Int) RSAKeyParameters {
return &rsaKeyParameters{
privateKey: isPrivate,
modulus: modulus,
exponent: exponent,
}
}
type rsaKeyParameters struct {
privateKey bool
modulus *big.Int
exponent *big.Int
}
func (r *rsaKeyParameters) Modulus() *big.Int { return r.modulus }
func (r *rsaKeyParameters) Exponent() *big.Int { return r.exponent }
func (r *rsaKeyParameters) Private() bool { return r.privateKey }
func NewRSAPrivateCrtKeyParameters(
modulus,
publicExponent,
privateExponent,
p,
q,
dP,
dQ,
qInv *big.Int) *RSAPrivateCrtKeyParameters {
return &RSAPrivateCrtKeyParameters{
RSAKeyParameters: NewRSAKeyParameters(true, modulus, privateExponent),
e: publicExponent,
p: p,
q: q,
dP: dP,
dQ: dQ,
qInv: qInv,
}
}
type RSAPrivateCrtKeyParameters struct {
RSAKeyParameters
e *big.Int
p *big.Int
q *big.Int
dP *big.Int
dQ *big.Int
qInv *big.Int
}
func (r *RSAPrivateCrtKeyParameters) PublicExponent() *big.Int { return r.e }
func (r *RSAPrivateCrtKeyParameters) P() *big.Int { return r.p }
func (r *RSAPrivateCrtKeyParameters) Q() *big.Int { return r.q }
func (r *RSAPrivateCrtKeyParameters) DP() *big.Int { return r.dP }
func (r *RSAPrivateCrtKeyParameters) DQ() *big.Int { return r.dQ }
func (r *RSAPrivateCrtKeyParameters) QInv() *big.Int { return r.qInv }
type RSAEngine struct {
*RSACoreEngine
}
func (r *RSAEngine) Init(forEncryption bool, key RSAKeyParameters) {
if r.RSACoreEngine == nil {
r.RSACoreEngine = newRsaCoreEngine()
}
r.RSACoreEngine.Init(forEncryption, key)
}
func (r *RSAEngine) ProcessBlock(in []byte, inOff, inLen int) []byte {
if r.RSACoreEngine == nil {
panic(fmt.Errorf("RAS engine not initialized"))
}
return r.RSACoreEngine.ConvertOutput(r.RSACoreEngine.ProcessBlock(r.RSACoreEngine.ConvertInput(in, inOff, inLen)))
}
func newRsaCoreEngine() *RSACoreEngine {
return &RSACoreEngine{}
}
type RSACoreEngine struct {
key RSAKeyParameters
forEncryption bool
}
func (r *RSACoreEngine) Init(forEncryption bool, key RSAKeyParameters) {
r.key = key
r.forEncryption = forEncryption
}
func (r *RSACoreEngine) InputBlockSize() int {
bitSize := r.key.Modulus().BitLen()
if r.forEncryption {
return (bitSize+7)/8 - 1
} else {
return (bitSize + 7) / 8
}
}
func (r *RSACoreEngine) OutputBlockSize() int {
bitSize := r.key.Modulus().BitLen()
if r.forEncryption {
return (bitSize + 7) / 8
} else {
return (bitSize+7)/8 - 1
}
}
func (r *RSACoreEngine) ConvertInput(in []byte, inOff, inLen int) *big.Int {
if inLen > (r.InputBlockSize() + 1) {
panic(fmt.Errorf("input too large for RSA cipher."))
} else if inLen == (r.InputBlockSize()+1) && !r.forEncryption {
panic(fmt.Errorf("input too large for RSA cipher."))
}
var block []byte
if inOff != 0 || inLen != len(in) {
block = make([]byte, inLen)
// System.arraycopy(in, inOff, block, 0, inLen);
arrayCopy(in, inOff, block, 0, inLen)
} else {
block = in
}
res := new(big.Int)
res = res.Abs(res.SetBytes(block))
if res.Cmp(r.key.Modulus()) >= 0 {
panic(fmt.Errorf("input too large for RSA cipher."))
}
return res
}
func (r *RSACoreEngine) ConvertOutput(result *big.Int) []byte {
output := result.Bytes()
if r.forEncryption {
if output[0] == 0 && len(output) > r.OutputBlockSize() {
// have ended up with an extra zero byte, copy down.
tmp := make([]byte, len(output)-1)
// System.arraycopy(output, 1, tmp, 0, tmp.length);
arrayCopy(output, 1, tmp, 0, len(tmp))
return tmp
}
if len(output) < r.OutputBlockSize() { // have ended up with less bytes than normal, lengthen
tmp := make([]byte, r.OutputBlockSize())
// System.arraycopy(output, 0, tmp, tmp.length - output.length, output.length);
arrayCopy(output, 0, tmp, len(tmp)-len(output), len(output))
return tmp
}
} else {
if output[0] == 0 { // have ended up with an extra zero byte, copy down.
tmp := make([]byte, len(output)-1)
// System.arraycopy(output, 1, tmp, 0, tmp.length);
arrayCopy(output, 1, tmp, 0, len(tmp))
return tmp
}
}
return output
}
func (r *RSACoreEngine) ProcessBlock(input *big.Int) *big.Int {
if crtKey, ok := r.key.(*RSAPrivateCrtKeyParameters); ok {
//
// we have the extra factors, use the Chinese Remainder Theorem - the author
// wishes to express his thanks to Dirk Bonekaemper at rtsffm.com for
// advice regarding the expression of this.
//
p := crtKey.P()
q := crtKey.Q()
dP := crtKey.DP()
dQ := crtKey.DQ()
qInv := crtKey.QInv()
var mP, mQ, h, m *big.Int
// mP = ((input mod p) ^ dP)) mod p
mP = mP.Exp(new(big.Int).Rem(input, p), dP, p)
// mQ = ((input mod q) ^ dQ)) mod q
mQ = mQ.Exp(new(big.Int).Rem(input, q), dQ, q)
// h = qInv * (mP - mQ) mod p
h = h.Sub(mP, mQ)
h = h.Mul(h, qInv)
h = h.Mod(h, p) // mod (in Java) returns the positive residual
// m = h * q + mQ
m = h.Mul(h, q)
m = m.Add(m, mQ)
return m
} else {
return new(big.Int).Exp(input, r.key.Exponent(), r.key.Modulus())
}
}
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