PublicKey from serialized bytes (#154)

* small fixes

* gofmt

* fix in raw tx build

* fixes after review

* balance getter interface

* moved address and signature calculation to public key

* errors handling

* PublicKey() returns PublicKey instead of bytes slice

* fixes after review

* fixes after review

* public key creation from asn1 serialized key

pkg/crypto/public_key.go

@@ -2,7 +2,9 @@ package crypto
 
 import (
 	"bytes"
+	"crypto/ecdsa"
 	"crypto/sha256"
+	"crypto/x509"
 	"encoding/binary"
 	"encoding/hex"
 	"io"
@@ -72,6 +74,28 @@ func (p *PublicKey) Bytes() []byte {
 	return append([]byte{prefix}, paddedX...)
 }
 
+// NewPublicKeyFromRawBytes returns a NEO PublicKey from the ASN.1 serialized keys.
+func NewPublicKeyFromRawBytes(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{
+		ECPoint{
+			X: pk.X,
+			Y: pk.Y,
+		},
+	}
+	return &key, nil
+}
+
 // DecodeBytes decodes a PublicKey from the given slice of bytes.
 func (p *PublicKey) DecodeBytes(data []byte) error {
 	l := len(data)
@@ -163,7 +187,7 @@ func (p *PublicKey) Signature() ([]byte, error) {
 func (p *PublicKey) Address() (string, error) {
 	var (
 		err error
-		b []byte
+		b   []byte
 	)
 	if b, err = p.Signature(); err != nil {
 		return "", err