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package oprf
import (
"encoding/binary"
"io"
"github.com/cloudflare/circl/group"
)
type PrivateKey struct {
p params
k group.Scalar
pub *PublicKey
}
type PublicKey struct {
p params
e group.Element
}
func (k *PrivateKey) MarshalBinary() ([]byte, error) { return k.k.MarshalBinary() }
func (k *PublicKey) MarshalBinary() ([]byte, error) { return k.e.MarshalBinaryCompress() }
func (k *PrivateKey) UnmarshalBinary(s Suite, data []byte) error {
p, ok := s.(params)
if !ok {
return ErrInvalidSuite
}
k.p = p
k.k = k.p.group.NewScalar()
return k.k.UnmarshalBinary(data)
}
func (k *PublicKey) UnmarshalBinary(s Suite, data []byte) error {
p, ok := s.(params)
if !ok {
return ErrInvalidSuite
}
k.p = p
k.e = k.p.group.NewElement()
return k.e.UnmarshalBinary(data)
}
func (k *PrivateKey) Public() *PublicKey {
if k.pub == nil {
k.pub = &PublicKey{k.p, k.p.group.NewElement().MulGen(k.k)}
}
return k.pub
}
// GenerateKey generates a private key compatible with the suite.
func GenerateKey(s Suite, rnd io.Reader) (*PrivateKey, error) {
if rnd == nil {
return nil, io.ErrNoProgress
}
p, ok := s.(params)
if !ok {
return nil, ErrInvalidSuite
}
privateKey := p.group.RandomScalar(rnd)
return &PrivateKey{p, privateKey, nil}, nil
}
// DeriveKey generates a private key from a 32-byte seed and an optional info string.
func DeriveKey(s Suite, mode Mode, seed, info []byte) (*PrivateKey, error) {
const maxTries = 255
p, ok := s.(params)
if !ok {
return nil, ErrInvalidSuite
}
if !isValidMode(mode) {
return nil, ErrInvalidMode
}
if len(seed) != 32 {
return nil, ErrInvalidSeed
}
p.m = mode
lenInfo := []byte{0, 0}
binary.BigEndian.PutUint16(lenInfo, uint16(len(info)))
deriveInput := append(append(append([]byte{}, seed...), lenInfo...), info...)
dst := p.getDST(deriveKeyPairDST)
zero := p.group.NewScalar()
privateKey := p.group.NewScalar()
for counter := byte(0); privateKey.IsEqual(zero); counter++ {
if counter > maxTries {
return nil, ErrDeriveKeyPairError
}
privateKey = p.group.HashToScalar(append(deriveInput, counter), dst)
}
return &PrivateKey{p, privateKey, nil}, nil
}
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