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110 lines
2.9 KiB
Go
110 lines
2.9 KiB
Go
package ecc
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import (
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"crypto/rand"
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"errors"
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"fmt"
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"io"
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"golang.org/x/crypto/curve25519"
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"go.mau.fi/libsignal/logger"
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)
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// DjbType is the Diffie-Hellman curve type (curve25519) created by D. J. Bernstein.
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const DjbType = 0x05
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var ErrBadKeyType = errors.New("bad key type")
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// DecodePoint will take the given bytes and offset and return an ECPublicKeyable object.
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// This is used to check the byte at the given offset in the byte array for a special
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// "type" byte that will determine the key type. Currently only DJB EC keys are supported.
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func DecodePoint(bytes []byte, offset int) (ECPublicKeyable, error) {
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keyType := bytes[offset] & 0xFF
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switch keyType {
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case DjbType:
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keyBytes := [32]byte{}
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copy(keyBytes[:], bytes[offset+1:])
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return NewDjbECPublicKey(keyBytes), nil
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default:
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return nil, fmt.Errorf("%w %d", ErrBadKeyType, keyType)
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}
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}
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func CreateKeyPair(privateKey []byte) *ECKeyPair {
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var private, public [32]byte
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copy(private[:], privateKey)
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private[0] &= 248
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private[31] &= 127
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private[31] |= 64
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curve25519.ScalarBaseMult(&public, &private)
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// Put data into our keypair struct
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djbECPub := NewDjbECPublicKey(public)
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djbECPriv := NewDjbECPrivateKey(private)
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keypair := NewECKeyPair(djbECPub, djbECPriv)
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logger.Debug("Returning keypair: ", keypair)
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return keypair
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}
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// GenerateKeyPair returns an EC Key Pair.
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func GenerateKeyPair() (*ECKeyPair, error) {
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// logger.Debug("Generating EC Key Pair...")
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// Get cryptographically secure random numbers.
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random := rand.Reader
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// Create a byte array for our public and private keys.
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var private, public [32]byte
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// Generate some random data
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_, err := io.ReadFull(random, private[:])
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if err != nil {
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return nil, err
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}
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// Documented at: http://cr.yp.to/ecdh.html
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private[0] &= 248
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private[31] &= 127
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private[31] |= 64
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curve25519.ScalarBaseMult(&public, &private)
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// Put data into our keypair struct
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djbECPub := NewDjbECPublicKey(public)
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djbECPriv := NewDjbECPrivateKey(private)
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keypair := NewECKeyPair(djbECPub, djbECPriv)
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// logger.Debug("Returning keypair: ", keypair)
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return keypair, nil
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}
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// VerifySignature verifies that the message was signed with the given key.
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func VerifySignature(signingKey ECPublicKeyable, message []byte, signature [64]byte) bool {
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logger.Debug("Verifying signature of bytes: ", message)
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publicKey := signingKey.PublicKey()
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valid := verify(publicKey, message, &signature)
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logger.Debug("Signature valid: ", valid)
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return valid
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}
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// CalculateSignature signs a message with the given private key.
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func CalculateSignature(signingKey ECPrivateKeyable, message []byte) [64]byte {
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logger.Debug("Signing bytes with signing key")
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// Get cryptographically secure random numbers.
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var random [64]byte
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r := rand.Reader
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io.ReadFull(r, random[:])
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// Get the private key.
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privateKey := signingKey.Serialize()
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// Sign the message.
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signature := sign(&privateKey, message, random)
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return *signature
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}
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