package key import ( "bytes" "crypto/sha512" "encoding/binary" "golang.org/x/crypto/ed25519" ) type Sec struct { PKAlg [2]byte KDFAlg [2]byte KDFRounds uint32 Salt [16]byte Checksum [8]byte KeyNum [8]byte Key [ed25519.PrivateKeySize]byte } // Sign message func (v *Sec) Sign(message []byte) *Sig { sig := &Sig{PKAlg: v.PKAlg, KeyNum: v.KeyNum} copy(sig.Sig[:], ed25519.Sign(ed25519.PrivateKey(v.Key[:]), message)) return sig } func (v *Sec) Validate() error { if v.PKAlg != pkAlg { return ErrInvalidPK } if v.KDFAlg != kdfAlg { return ErrInvalidKDF } sum := sha512.Sum512(v.Key[:]) if !bytes.Equal(sum[:len(v.Checksum)], v.Checksum[:]) { return ErrInvalidKey } return nil } // Public key of secret key func (v *Sec) Public() *Pub { key := ed25519.PrivateKey(v.Key[:]).Public().(ed25519.PublicKey) pub := &Pub{PKAlg: pkAlg, KeyNum: v.KeyNum} copy(pub.Key[:], key) return pub } func (v *Sec) Crypt(der Deriver) error { if der == nil || v.KDFRounds == 0 { return nil } xor, err := der.Derive(v.Salt[:], int(v.KDFRounds), len(v.Key)) if err != nil { return err } for i := range xor { v.Key[i] ^= xor[i] } return nil } // NewSec returns a parsed and decoded secret key func NewSec(data []byte, der Deriver) (*Sec, error) { sec := new(Sec) if err := sec.UnmarshalBinary(data); err != nil { return nil, err } if err := sec.Crypt(der); err != nil { return nil, err } return sec, sec.Validate() } func (v *Sec) MarshalBinary() ([]byte, error) { buf := new(bytes.Buffer) if err := binary.Write(buf, binary.BigEndian, v); err != nil { return nil, err } return buf.Bytes(), nil } func (v *Sec) UnmarshalBinary(data []byte) error { buf := bytes.NewReader(data) return binary.Read(buf, binary.BigEndian, v) }