46 lines
1.1 KiB
Go
46 lines
1.1 KiB
Go
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package crypto
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import (
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"crypto/rand"
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"errors"
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"golang.org/x/crypto/curve25519"
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)
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// KeyExchange manages the exchange of keys
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type curve25519KEX struct {
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secret [32]byte
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public [32]byte
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}
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var _ KeyExchange = &curve25519KEX{}
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// NewCurve25519KEX creates a new KeyExchange using Curve25519, see https://cr.yp.to/ecdh.html
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func NewCurve25519KEX() (KeyExchange, error) {
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c := &curve25519KEX{}
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if _, err := rand.Read(c.secret[:]); err != nil {
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return nil, errors.New("Curve25519: could not create private key")
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}
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// See https://cr.yp.to/ecdh.html
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c.secret[0] &= 248
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c.secret[31] &= 127
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c.secret[31] |= 64
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curve25519.ScalarBaseMult(&c.public, &c.secret)
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return c, nil
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}
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func (c *curve25519KEX) PublicKey() []byte {
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return c.public[:]
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}
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func (c *curve25519KEX) CalculateSharedKey(otherPublic []byte) ([]byte, error) {
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if len(otherPublic) != 32 {
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return nil, errors.New("Curve25519: expected public key of 32 byte")
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}
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var res [32]byte
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var otherPublicArray [32]byte
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copy(otherPublicArray[:], otherPublic)
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curve25519.ScalarMult(&res, &c.secret, &otherPublicArray)
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return res[:], nil
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}
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