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package key
import (
"bytes"
"crypto/sha512"
"golang.org/x/crypto/ed25519"
)
type Enc struct {
PKAlg [2]byte
KDFAlg [2]byte
KDFRounds uint32
Salt [16]byte
Checksum [8]byte
KeyNum [8]byte
Key [ed25519.PrivateKeySize]byte
}
func (v *Enc) 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 *Enc) Check() 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
}
func (v *Enc) MarshalBinary() ([]byte, error) {
return Marshal(v)
}
func (v *Enc) UnmarshalBinary(data []byte) error {
return Unmarshal(data, v)
}
func ParseEnc(data []byte, d KeyDeriver) (*Enc, error) {
var enc *Enc
if err := enc.UnmarshalBinary(data); err != nil {
return nil, err
}
if d != nil && enc.KDFRounds > 0 {
xor, err := d.DeriveKey(enc.Salt[:], int(enc.KDFRounds), len(enc.Key))
if err != nil {
return nil, err
}
for i := range xor {
enc.Key[i] ^= xor[i]
}
}
return enc, enc.Check()
}
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