From 002394c1237d958a6aab7dd31228afc466b42012 Mon Sep 17 00:00:00 2001
From: recanman <29310982+recanman@users.noreply.github.com>
Date: Tue, 4 Jun 2024 18:59:09 -0700
Subject: [PATCH] test: ed25519 public key

---
 src/Ed25519.php            |  9 +++++++++
 tests/unit/Ed25519Test.php | 11 +++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/Ed25519.php b/src/Ed25519.php
index d324f11..a1fc68a 100644
--- a/src/Ed25519.php
+++ b/src/Ed25519.php
@@ -259,6 +259,15 @@ public function Hint(mixed $m, bool $asBigInt = false): BigInteger|string
         return $asBigInt ? $res : $res->toDec();
     }
 
+    /**
+     * Determines the public key from a secret key.
+     */
+    public function publickey(BigInteger $sk): string
+    {
+        return $this->encodePoint($this->scalarmult($this->B, $sk));
+    }
+
+
     /**
      * Determines if a point is on the Edwards25519 curve.
      */
diff --git a/tests/unit/Ed25519Test.php b/tests/unit/Ed25519Test.php
index d0a285c..ce48870 100644
--- a/tests/unit/Ed25519Test.php
+++ b/tests/unit/Ed25519Test.php
@@ -25,6 +25,9 @@ class Ed25519Test extends TestCase
     private $testEncodedB = "5866666666666666666666666666666666666666666666666666666666666666";
     private $testBitInput = "fffffffffffffffffffffffffffffffX";
 
+    private $testPublicKeyInput = "92109952688507622152061303160978719049325098095664035905533631729165308545803";
+    private $testPublicKeyOutput = "22b93c70919f3bb0023e2dd172db4b0d1ed9980fa1edf8cfdd39181047f66639";
+
     private $testEdwardsOutput = "c9a3f86aae465f0e56513864510f3997561fa2c9e85ea21dc2292309f3cd6022";
 
     protected function setUp(): void
@@ -97,6 +100,14 @@ public function testScalarMult(): void
         $this->assertEquals($this->ed25519->edwards($this->ed25519->B, $this->ed25519->B), $result);
     }
 
+    public function testPublicKey(): void
+    {
+        $sk = new BigInteger($this->testPublicKeyInput);
+        $pk = $this->ed25519->publickey($sk);
+
+        $this->assertEquals($this->testPublicKeyOutput, $pk);
+    }
+
     public function testEncodeInt(): void
     {
         $result = $this->ed25519->encodeint(new BigInteger(100));