Merge pull request #62 from cubemaze/cmd_x25519

feat: add command for generating a key pair for x25519 key exchange.

cmd/x25519.go

@@ -0,0 +1,52 @@
+package cmd
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"github.com/spf13/cobra"
+	"golang.org/x/crypto/curve25519"
+)
+
+var x25519Command = cobra.Command{
+	Use:   "x25519",
+	Short: "Generate key pair for x25519 key exchange",
+	Run: func(cmd *cobra.Command, args []string) {
+		executeX25519()
+	},
+}
+
+func init() {
+	command.AddCommand(&x25519Command)
+}
+
+func executeX25519() {
+	var output string
+	var err error
+	var privateKey []byte
+	var publicKey []byte
+
+	privateKey = make([]byte, curve25519.ScalarSize)
+	if _, err = rand.Read(privateKey); err != nil {
+		output = err.Error()
+		goto out
+	}
+
+	// Modify random bytes using algorithm described at:
+	// https://cr.yp.to/ecdh.html.
+	privateKey[0] &= 248
+	privateKey[31] &= 127
+	privateKey[31] |= 64
+
+	if publicKey, err = curve25519.X25519(privateKey, curve25519.Basepoint); err != nil {
+		output = err.Error()
+		goto out
+	}
+
+	output = fmt.Sprintf("Private key: %v\nPublic key: %v",
+		base64.RawURLEncoding.EncodeToString(privateKey),
+		base64.RawURLEncoding.EncodeToString(publicKey))
+
+out:
+	fmt.Println(output)
+}