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utils.go
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/
utils.go
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package multiformat
import (
"crypto/elliptic"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
bls12381 "github.com/kilic/bls12-381"
"github.com/multiformats/go-multibase"
"github.com/multiformats/go-varint"
)
const (
secp256k1KeyType = 0xe7
bls12p381g1KeyType = 0xea
bls12p381g2KeyType = 0xeb
)
// SerializePublicKey serialises a non-serialised multibase encoded multicodec identified EC public key
// For details on usage see specs https://specs.status.im/spec/2#public-key-serialization
func SerializePublicKey(key, outputBase string) (string, error) {
dKey, err := multibaseDecode(key)
if err != nil {
return "", err
}
kt, i, err := getPublicKeyType(dKey)
if err != nil {
return "", err
}
cpk, err := compressPublicKey(dKey[i:], kt)
if err != nil {
return "", err
}
cpk = prependKeyIdentifier(cpk, kt, i)
return multibaseEncode(outputBase, cpk)
}
// DeserializePublicKey deserialise a serialised multibase encoded multicodec identified EC public key
// For details on usage see specs https://specs.status.im/spec/2#public-key-serialization
func DeserializePublicKey(key, outputBase string) (string, error) {
cpk, err := multibaseDecode(key)
if err != nil {
return "", err
}
kt, i, err := getPublicKeyType(cpk)
if err != nil {
return "", err
}
pk, err := decompressPublicKey(cpk[i:], kt)
if err != nil {
return "", err
}
pk = prependKeyIdentifier(pk, kt, i)
return multibaseEncode(outputBase, pk)
}
// getPublicKeyType wrapper for the `varint.FromUvarint()` func
func getPublicKeyType(key []byte) (uint64, int, error) {
return varint.FromUvarint(key)
}
// prependKeyIdentifier prepends an Unsigned Variable Integer (uvarint) to a given []byte
func prependKeyIdentifier(key []byte, kt uint64, ktl int) []byte {
buf := make([]byte, ktl)
varint.PutUvarint(buf, kt)
key = append(buf, key...)
return key
}
// compressPublicKey serves as logic switch function to parse key data for compression based on the given keyType
func compressPublicKey(key []byte, keyType uint64) ([]byte, error) {
switch keyType {
case secp256k1KeyType:
return compressSecp256k1PublicKey(key)
case bls12p381g1KeyType:
return compressBls12p381g1PublicKey(key)
case bls12p381g2KeyType:
return compressBls12p381g2PublicKey(key)
default:
return nil, fmt.Errorf("unsupported public key type '%X'", keyType)
}
}
// compressSecp256k1PublicKey is a dedicated key compression function for secp256k1 pks
func compressSecp256k1PublicKey(key []byte) ([]byte, error) {
x, y := elliptic.Unmarshal(secp256k1.S256(), key)
if err := isSecp256k1XYValid(key, x, y); err != nil {
return nil, err
}
cpk := secp256k1.CompressPubkey(x, y)
return cpk, nil
}
// compressBls12p381g1PublicKey is a dedicated key compression function for bls12 381 g1 pks
func compressBls12p381g1PublicKey(key []byte) ([]byte, error) {
g1 := bls12381.NewG1()
// Generate the G1 point
pg1, err := g1.FromBytes(key)
if err != nil {
return nil, err
}
cpk := g1.ToCompressed(pg1)
return cpk, nil
}
// compressBls12p381g1PublicKey is a dedicated key compression function for bls12 381 g2 pks
func compressBls12p381g2PublicKey(key []byte) ([]byte, error) {
g2 := bls12381.NewG2()
// Generate the G2 point
pg2, err := g2.FromBytes(key)
if err != nil {
return nil, err
}
cpk := g2.ToCompressed(pg2)
return cpk, nil
}
// decompressPublicKey serves as logic switch function to parse key data for decompression based on the given keyType
func decompressPublicKey(key []byte, keyType uint64) ([]byte, error) {
switch keyType {
case secp256k1KeyType:
return decompressSecp256k1PublicKey(key)
case bls12p381g1KeyType:
return decompressBls12p381g1PublicKey(key)
case bls12p381g2KeyType:
return decompressBls12p381g2PublicKey(key)
default:
return nil, fmt.Errorf("unsupported public key type '%X'", keyType)
}
}
// decompressSecp256k1PublicKey is a dedicated key decompression function for secp256k1 pks
func decompressSecp256k1PublicKey(key []byte) ([]byte, error) {
x, y := secp256k1.DecompressPubkey(key)
if err := isSecp256k1XYValid(key, x, y); err != nil {
return nil, err
}
k := elliptic.Marshal(secp256k1.S256(), x, y)
return k, nil
}
// isSecp256k1XYValid checks if a given x and y coordinate is nil, returns an error if either x or y is nil
// secp256k1.DecompressPubkey will not return an error if a compressed pk fails decompression and instead returns
// nil x, y coordinates
func isSecp256k1XYValid(key []byte, x, y *big.Int) error {
if x == nil || y == nil {
return fmt.Errorf("invalid public key format, '%b'", key)
}
return nil
}
// decompressBls12p381g1PublicKey is a dedicated key decompression function for bls12 381 g1 pks
func decompressBls12p381g1PublicKey(key []byte) ([]byte, error) {
g1 := bls12381.NewG1()
pg1, err := g1.FromCompressed(key)
if err != nil {
return nil, err
}
pk := g1.ToUncompressed(pg1)
return pk, nil
}
// decompressBls12p381g2PublicKey is a dedicated key decompression function for bls12 381 g2 pks
func decompressBls12p381g2PublicKey(key []byte) ([]byte, error) {
g2 := bls12381.NewG2()
pg2, err := g2.FromCompressed(key)
if err != nil {
return nil, err
}
pk := g2.ToUncompressed(pg2)
return pk, nil
}
// multibaseEncode wraps `multibase.Encode()` extending the base functionality to support `0x` prefixed strings
func multibaseEncode(base string, data []byte) (string, error) {
if base == "0x" {
base = "f"
}
return multibase.Encode(multibase.Encoding(base[0]), data)
}
// multibaseDecode wraps `multibase.Decode()` extending the base functionality to support `0x` prefixed strings
func multibaseDecode(data string) ([]byte, error) {
if data[0:2] == "0x" {
data = "f" + data[2:]
}
_, dd, err := multibase.Decode(data)
return dd, err
}