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// Package ed25519 implements the ed25519 signature algorithm for OpenPGP
// as defined in the Open PGP crypto refresh.
package ed25519
import (
"crypto/subtle"
"io"
"github.com/ProtonMail/go-crypto/openpgp/errors"
ed25519lib "github.com/cloudflare/circl/sign/ed25519"
)
const (
// PublicKeySize is the size, in bytes, of public keys in this package.
PublicKeySize = ed25519lib.PublicKeySize
// SeedSize is the size, in bytes, of private key seeds.
// The private key representation used by RFC 8032.
SeedSize = ed25519lib.SeedSize
// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
SignatureSize = ed25519lib.SignatureSize
)
type PublicKey struct {
// Point represents the elliptic curve point of the public key.
Point []byte
}
type PrivateKey struct {
PublicKey
// Key the private key representation by RFC 8032,
// encoded as seed | pub key point.
Key []byte
}
// NewPublicKey creates a new empty ed25519 public key.
func NewPublicKey() *PublicKey {
return &PublicKey{}
}
// NewPrivateKey creates a new empty private key referencing the public key.
func NewPrivateKey(key PublicKey) *PrivateKey {
return &PrivateKey{
PublicKey: key,
}
}
// Seed returns the ed25519 private key secret seed.
// The private key representation by RFC 8032.
func (pk *PrivateKey) Seed() []byte {
return pk.Key[:SeedSize]
}
// MarshalByteSecret returns the underlying 32 byte seed of the private key.
func (pk *PrivateKey) MarshalByteSecret() []byte {
return pk.Seed()
}
// UnmarshalByteSecret computes the private key from the secret seed
// and stores it in the private key object.
func (sk *PrivateKey) UnmarshalByteSecret(seed []byte) error {
sk.Key = ed25519lib.NewKeyFromSeed(seed)
return nil
}
// GenerateKey generates a fresh private key with the provided randomness source.
func GenerateKey(rand io.Reader) (*PrivateKey, error) {
publicKey, privateKey, err := ed25519lib.GenerateKey(rand)
if err != nil {
return nil, err
}
privateKeyOut := new(PrivateKey)
privateKeyOut.PublicKey.Point = publicKey[:]
privateKeyOut.Key = privateKey[:]
return privateKeyOut, nil
}
// Sign signs a message with the ed25519 algorithm.
// priv MUST be a valid key! Check this with Validate() before use.
func Sign(priv *PrivateKey, message []byte) ([]byte, error) {
return ed25519lib.Sign(priv.Key, message), nil
}
// Verify verifies an ed25519 signature.
func Verify(pub *PublicKey, message []byte, signature []byte) bool {
return ed25519lib.Verify(pub.Point, message, signature)
}
// Validate checks if the ed25519 private key is valid.
func Validate(priv *PrivateKey) error {
expectedPrivateKey := ed25519lib.NewKeyFromSeed(priv.Seed())
if subtle.ConstantTimeCompare(priv.Key, expectedPrivateKey) == 0 {
return errors.KeyInvalidError("ed25519: invalid ed25519 secret")
}
if subtle.ConstantTimeCompare(priv.PublicKey.Point, expectedPrivateKey[SeedSize:]) == 0 {
return errors.KeyInvalidError("ed25519: invalid ed25519 public key")
}
return nil
}
// ENCODING/DECODING signature:
// WriteSignature encodes and writes an ed25519 signature to writer.
func WriteSignature(writer io.Writer, signature []byte) error {
_, err := writer.Write(signature)
return err
}
// ReadSignature decodes an ed25519 signature from a reader.
func ReadSignature(reader io.Reader) ([]byte, error) {
signature := make([]byte, SignatureSize)
if _, err := io.ReadFull(reader, signature); err != nil {
return nil, err
}
return signature, nil
}
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