96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
package crypto
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import (
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"crypto/ecdsa"
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"crypto/rand"
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"crypto/sha256"
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"crypto/sha512"
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"errors"
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"github.com/oasisprotocol/curve25519-voi/curve"
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"github.com/oasisprotocol/curve25519-voi/curve/scalar"
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)
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var errInvalidKeyLength = errors.New("invalid key length")
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const (
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curve25519KeySize = 32
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clampMaskLow = 248
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clampMaskHigh = 127
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clampHighBit = 64
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sharedSignBit = 0x80
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privateKeyTopMask = 0x7F
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)
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func GenerateTemporaryKey() ([]byte, []byte, error) {
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privateKey := make([]byte, curve25519KeySize)
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_, err := rand.Read(privateKey)
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if err != nil {
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return nil, nil, err
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}
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ClampScalar(privateKey)
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sc, err := scalar.NewFromBits(privateKey)
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if err != nil {
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return nil, nil, err
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}
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publicKey, err := curve.NewEdwardsPoint().MulBasepoint(curve.ED25519_BASEPOINT_TABLE, sc).MarshalBinary()
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if err != nil {
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return nil, nil, err
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}
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return publicKey, privateKey, nil
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}
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func Sign(priv *ecdsa.PrivateKey, data []byte) ([]byte, error) {
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hash := sha256.Sum256(data)
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return ecdsa.SignASN1(rand.Reader, priv, hash[:])
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}
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func VerifySign(pub *ecdsa.PublicKey, data, sig []byte) bool {
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hash := sha256.Sum256(data)
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return ecdsa.VerifyASN1(pub, hash[:], sig)
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}
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func ClampScalar(key []byte) {
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if len(key) < curve25519KeySize {
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return
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}
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key[0] &= clampMaskLow
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key[curve25519KeySize-1] &= clampMaskHigh
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key[curve25519KeySize-1] |= clampHighBit
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}
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func GetSharedSecret2(publicKey, privateKey []byte) ([]byte, error) {
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if len(publicKey) != curve25519KeySize || len(privateKey) != curve25519KeySize {
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return nil, errInvalidKeyLength
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}
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privateKeyCpy := make([]byte, curve25519KeySize)
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copy(privateKeyCpy, privateKey)
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privateKeyCpy[curve25519KeySize-1] &= privateKeyTopMask
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sc, err := scalar.NewFromBits(privateKeyCpy)
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if err != nil {
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return nil, err
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}
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pub := curve.NewEdwardsPoint()
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err = pub.UnmarshalBinary(publicKey)
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if err != nil {
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return nil, err
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}
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pub.Neg(pub)
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sharedPoint := curve.NewEdwardsPoint().Mul(pub, sc)
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shared, err := sharedPoint.MarshalBinary()
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if err != nil {
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return nil, err
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}
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shared[curve25519KeySize-1] ^= sharedSignBit
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hash := sha512.Sum512(shared)
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return hash[:], nil
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}
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