From 83e87c2cf4243293506e9d149641918773be4f53 Mon Sep 17 00:00:00 2001
From: Vitor Pamplona <vitor@vitorpamplona.com>
Date: Tue, 16 Sep 2025 17:06:01 -0400
Subject: [PATCH] Adds an event id hash check that doesn't create a separate
 bytearray to compare between the incoming hex from the relay and the
 recalculated byte array from SHA256.

---
 .../quartz/benchmark/HexBenchmark.kt            |  7 +++++++
 .../vitorpamplona/quartz/nip01Core/EventExt.kt  |  2 +-
 .../quartz/nip01Core/crypto/EventHasher.kt      | 15 ++++++++++++++-
 .../com/vitorpamplona/quartz/utils/Hex.kt       | 17 +++++++++++++++++
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/HexBenchmark.kt b/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/HexBenchmark.kt
index bb1272d4e..e4553ade8 100644
--- a/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/HexBenchmark.kt
+++ b/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/HexBenchmark.kt
@@ -43,6 +43,13 @@ class HexBenchmark {
         fr.acinq.secp256k1.Hex
             .decode(hex)
 
+    @Test
+    fun hexIsEqual() {
+        r.measureRepeated {
+            assert(Hex.isEqual(hex, bytes))
+        }
+    }
+
     @Test
     fun hexDecodeOurs() {
         r.measureRepeated {
diff --git a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/EventExt.kt b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/EventExt.kt
index 81e828a65..a5cd423e0 100644
--- a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/EventExt.kt
+++ b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/EventExt.kt
@@ -30,7 +30,7 @@ fun Event.generateId(): String = EventHasher.hashId(pubKey, createdAt, kind, tag
 
 fun Event.verifyId(): Boolean {
     if (id.isEmpty()) return false
-    return id == generateId()
+    return EventHasher.hashIdEquals(id, pubKey, createdAt, kind, tags, content)
 }
 
 fun Event.verifySignature(): Boolean {
diff --git a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/crypto/EventHasher.kt b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/crypto/EventHasher.kt
index 5fcfd9e8c..c5e2e3fd3 100644
--- a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/crypto/EventHasher.kt
+++ b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/nip01Core/crypto/EventHasher.kt
@@ -25,6 +25,7 @@ import com.fasterxml.jackson.databind.node.JsonNodeFactory
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.toHexKey
 import com.vitorpamplona.quartz.nip01Core.jackson.JsonMapper
+import com.vitorpamplona.quartz.utils.Hex
 import com.vitorpamplona.quartz.utils.sha256.sha256
 
 class EventHasher {
@@ -80,5 +81,17 @@ class EventHasher {
             tags: Array<Array<String>>,
             content: String,
         ): String = hashIdBytes(pubKey, createdAt, kind, tags, content).toHexKey()
+
+        fun hashIdEquals(
+            id: HexKey,
+            pubKey: HexKey,
+            createdAt: Long,
+            kind: Int,
+            tags: Array<Array<String>>,
+            content: String,
+        ): Boolean {
+            val outId = hashIdBytes(pubKey, createdAt, kind, tags, content)
+            return Hex.isEqual(id, outId)
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/Hex.kt b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/Hex.kt
index 270d66a5e..0ff6eec22 100644
--- a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/Hex.kt
+++ b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/Hex.kt
@@ -74,4 +74,21 @@ object Hex {
         }
         return String(out)
     }
+
+    fun isEqual(
+        id: String,
+        ourId: ByteArray,
+    ): Boolean {
+        var charIndex = 0
+        for (i in 0 until ourId.size) {
+            val chars = byteToHex[ourId[i].toInt() and 0xFF]
+            if (
+                id[charIndex++] != (chars shr 8).toChar() ||
+                id[charIndex++] != (chars and 0xFF).toChar()
+            ) {
+                return false
+            }
+        }
+        return true
+    }
 }