package keys import ( "bytes" "crypto/ecdsa" "crypto/elliptic" "crypto/x509" "encoding/hex" "fmt" "math/big" "github.com/CityOfZion/neo-go/pkg/crypto" "github.com/CityOfZion/neo-go/pkg/crypto/hash" "github.com/CityOfZion/neo-go/pkg/io" "github.com/pkg/errors" ) // PublicKeys is a list of public keys. type PublicKeys []*PublicKey func (keys PublicKeys) Len() int { return len(keys) } func (keys PublicKeys) Swap(i, j int) { keys[i], keys[j] = keys[j], keys[i] } func (keys PublicKeys) Less(i, j int) bool { if keys[i].X.Cmp(keys[j].X) == -1 { return true } if keys[i].X.Cmp(keys[j].X) == 1 { return false } if keys[i].X.Cmp(keys[j].X) == 0 { return false } return keys[i].Y.Cmp(keys[j].Y) == -1 } // PublicKey represents a public key and provides a high level // API around the X/Y point. type PublicKey struct { X *big.Int Y *big.Int } // NewPublicKeyFromString returns a public key created from the // given hex string. func NewPublicKeyFromString(s string) (*PublicKey, error) { b, err := hex.DecodeString(s) if err != nil { return nil, err } pubKey := new(PublicKey) r := io.NewBinReaderFromBuf(b) pubKey.DecodeBinary(r) if r.Err != nil { return nil, r.Err } return pubKey, nil } // Bytes returns the byte array representation of the public key. func (p *PublicKey) Bytes() []byte { if p.IsInfinity() { return []byte{0x00} } var ( x = p.X.Bytes() paddedX = append(bytes.Repeat([]byte{0x00}, 32-len(x)), x...) prefix = byte(0x03) ) if p.Y.Bit(0) == 0 { prefix = byte(0x02) } return append([]byte{prefix}, paddedX...) } // NewPublicKeyFromASN1 returns a NEO PublicKey from the ASN.1 serialized key. func NewPublicKeyFromASN1(data []byte) (*PublicKey, error) { var ( err error pubkey interface{} ) if pubkey, err = x509.ParsePKIXPublicKey(data); err != nil { return nil, err } pk, ok := pubkey.(*ecdsa.PublicKey) if !ok { return nil, errors.New("given bytes aren't ECDSA public key") } key := PublicKey{ X: pk.X, Y: pk.Y, } return &key, nil } // decodeCompressedY performs decompression of Y coordinate for given X and Y's least significant bit. func decodeCompressedY(x *big.Int, ylsb uint) (*big.Int, error) { c := elliptic.P256() cp := c.Params() three := big.NewInt(3) /* y**2 = x**3 + a*x + b % p */ xCubed := new(big.Int).Exp(x, three, cp.P) threeX := new(big.Int).Mul(x, three) threeX.Mod(threeX, cp.P) ySquared := new(big.Int).Sub(xCubed, threeX) ySquared.Add(ySquared, cp.B) ySquared.Mod(ySquared, cp.P) y := new(big.Int).ModSqrt(ySquared, cp.P) if y == nil { return nil, errors.New("error computing Y for compressed point") } if y.Bit(0) != ylsb { y.Neg(y) y.Mod(y, cp.P) } return y, nil } // DecodeBytes decodes a PublicKey from the given slice of bytes. func (p *PublicKey) DecodeBytes(data []byte) error { b := io.NewBinReaderFromBuf(data) p.DecodeBinary(b) return b.Err } // DecodeBinary decodes a PublicKey from the given BinReader. func (p *PublicKey) DecodeBinary(r *io.BinReader) { var prefix uint8 var x, y *big.Int var err error r.ReadLE(&prefix) if r.Err != nil { return } // Infinity switch prefix { case 0x00: // noop, initialized to nil return case 0x02, 0x03: // Compressed public keys xbytes := make([]byte, 32) r.ReadLE(xbytes) if r.Err != nil { return } x = new(big.Int).SetBytes(xbytes) ylsb := uint(prefix & 0x1) y, err = decodeCompressedY(x, ylsb) if err != nil { return } case 0x04: xbytes := make([]byte, 32) ybytes := make([]byte, 32) r.ReadLE(xbytes) r.ReadLE(ybytes) if r.Err != nil { return } x = new(big.Int).SetBytes(xbytes) y = new(big.Int).SetBytes(ybytes) default: r.Err = errors.Errorf("invalid prefix %d", prefix) return } c := elliptic.P256() cp := c.Params() if !c.IsOnCurve(x, y) { r.Err = errors.New("enccoded point is not on the P256 curve") return } if x.Cmp(cp.P) >= 0 || y.Cmp(cp.P) >= 0 { r.Err = errors.New("enccoded point is not correct (X or Y is bigger than P") return } p.X, p.Y = x, y } // EncodeBinary encodes a PublicKey to the given BinWriter. func (p *PublicKey) EncodeBinary(w *io.BinWriter) { w.WriteLE(p.Bytes()) } // Signature returns a NEO-specific hash of the key. func (p *PublicKey) Signature() []byte { b := p.Bytes() b = append([]byte{0x21}, b...) b = append(b, 0xAC) sig := hash.Hash160(b) return sig.Bytes() } // Address returns a base58-encoded NEO-specific address based on the key hash. func (p *PublicKey) Address() string { var b = p.Signature() b = append([]byte{0x17}, b...) return crypto.Base58CheckEncode(b) } // Verify returns true if the signature is valid and corresponds // to the hash and public key. func (p *PublicKey) Verify(signature []byte, hash []byte) bool { publicKey := &ecdsa.PublicKey{} publicKey.Curve = elliptic.P256() publicKey.X = p.X publicKey.Y = p.Y if p.X == nil || p.Y == nil { return false } rBytes := new(big.Int).SetBytes(signature[0:32]) sBytes := new(big.Int).SetBytes(signature[32:64]) return ecdsa.Verify(publicKey, hash, rBytes, sBytes) } // IsInfinity checks if the key is infinite (null, basically). func (p *PublicKey) IsInfinity() bool { return p.X == nil && p.Y == nil } // String implements the Stringer interface. func (p *PublicKey) String() string { if p.IsInfinity() { return "00" } bx := hex.EncodeToString(p.X.Bytes()) by := hex.EncodeToString(p.Y.Bytes()) return fmt.Sprintf("%s%s", bx, by) }