mihomo/component/generator/x25519.go

88 lines
2.1 KiB
Go

package generator
import (
"crypto/ecdh"
"crypto/rand"
"encoding/hex"
"filippo.io/edwards25519"
)
const X25519KeySize = 32
func GenX25519PrivateKey() (*ecdh.PrivateKey, error) {
var privateKey [X25519KeySize]byte
_, err := rand.Read(privateKey[:])
if err != nil {
return nil, err
}
// Avoid generating equivalent X25519 private keys
// https://github.com/XTLS/Xray-core/pull/1747
//
// Modify random bytes using algorithm described at:
// https://cr.yp.to/ecdh.html.
privateKey[0] &= 248
privateKey[31] &= 127
privateKey[31] |= 64
return ecdh.X25519().NewPrivateKey(privateKey[:])
}
// GenerateSudokuMasterKey generates a random master private key (scalar) and its public key (point)
func GenerateSudokuMasterKey() (*edwards25519.Scalar, *edwards25519.Point, error) {
// 1. Generate random scalar x (32 bytes)
var seed [64]byte
if _, err := rand.Read(seed[:]); err != nil {
return nil, nil, err
}
x, err := edwards25519.NewScalar().SetUniformBytes(seed[:])
if err != nil {
return nil, nil, err
}
// 2. Calculate Public Key P = x * G
P := new(edwards25519.Point).ScalarBaseMult(x)
return x, P, nil
}
// SplitSudokuPrivateKey takes a master private key x and returns a new random split key (r, k)
// such that x = r + k (mod L).
// Returns hex encoded string of r || k (64 bytes)
func SplitSudokuPrivateKey(x *edwards25519.Scalar) (string, error) {
// 1. Generate random r (32 bytes)
var seed [64]byte
if _, err := rand.Read(seed[:]); err != nil {
return "", err
}
r, err := edwards25519.NewScalar().SetUniformBytes(seed[:])
if err != nil {
return "", err
}
// 2. Calculate k = x - r (mod L)
k := new(edwards25519.Scalar).Subtract(x, r)
// 3. Encode r and k
rBytes := r.Bytes()
kBytes := k.Bytes()
full := make([]byte, 64)
copy(full[:32], rBytes)
copy(full[32:], kBytes)
return hex.EncodeToString(full), nil
}
// EncodeSudokuPoint returns the hex string of the compressed point
func EncodeSudokuPoint(p *edwards25519.Point) string {
return hex.EncodeToString(p.Bytes())
}
// EncodeSudokuScalar returns the hex string of the scalar
func EncodeSudokuScalar(s *edwards25519.Scalar) string {
return hex.EncodeToString(s.Bytes())
}