88 lines
1.8 KiB
Go
88 lines
1.8 KiB
Go
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package ecdh
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import (
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"crypto"
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"crypto/elliptic"
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"io"
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"math/big"
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)
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type ellipticECDH struct {
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ECDH
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curve elliptic.Curve
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}
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type ellipticPublicKey struct {
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elliptic.Curve
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X, Y *big.Int
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}
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type ellipticPrivateKey struct {
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D []byte
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}
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// NewEllipticECDH creates a new instance of ECDH with the given elliptic.Curve curve
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// to use as the elliptical curve for elliptical curve diffie-hellman.
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func NewEllipticECDH(curve elliptic.Curve) ECDH {
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return &ellipticECDH{
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curve: curve,
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}
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}
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func (e *ellipticECDH) GenerateKey(rand io.Reader) (crypto.PrivateKey, crypto.PublicKey, error) {
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var d []byte
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var x, y *big.Int
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var priv *ellipticPrivateKey
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var pub *ellipticPublicKey
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var err error
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d, x, y, err = elliptic.GenerateKey(e.curve, rand)
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if err != nil {
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return nil, nil, err
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}
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priv = &ellipticPrivateKey{
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D: d,
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}
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pub = &ellipticPublicKey{
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Curve: e.curve,
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X: x,
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Y: y,
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}
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return priv, pub, nil
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}
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func (e *ellipticECDH) Marshal(p crypto.PublicKey) []byte {
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pub := p.(*ellipticPublicKey)
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return elliptic.Marshal(e.curve, pub.X, pub.Y)
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}
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func (e *ellipticECDH) Unmarshal(data []byte) (crypto.PublicKey, bool) {
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var key *ellipticPublicKey
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var x, y *big.Int
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x, y = elliptic.Unmarshal(e.curve, data)
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if x == nil || y == nil {
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return key, false
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}
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key = &ellipticPublicKey{
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Curve: e.curve,
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X: x,
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Y: y,
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}
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return key, true
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}
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// GenerateSharedSecret takes in a public key and a private key
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// and generates a shared secret.
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//
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// RFC5903 Section 9 states we should only return x.
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func (e *ellipticECDH) GenerateSharedSecret(privKey crypto.PrivateKey, pubKey crypto.PublicKey) ([]byte, error) {
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priv := privKey.(*ellipticPrivateKey)
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pub := pubKey.(*ellipticPublicKey)
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x, _ := e.curve.ScalarMult(pub.X, pub.Y, priv.D)
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return x.Bytes(), nil
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}
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