diff --git a/.coderabbit.yaml b/.coderabbit.yaml
new file mode 100644
index 0000000..44cb754
--- /dev/null
+++ b/.coderabbit.yaml
@@ -0,0 +1,18 @@
+# yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json
+language: en-US
+reviews:
+  profile: assertive
+  auto_review:
+    enabled: true
+    drafts: true
+    base_branches:
+      - main
+  request_changes_workflow: false
+  path_filters:
+    - "!**/target/**"
+    - "!**/build/**"
+    - "!**/node_modules/**"
+chat:
+  auto_reply: false
+knowledge_base:
+  opt_out: true
diff --git a/build.gradle.kts b/build.gradle.kts
index 0014394..b1b480c 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -31,7 +31,7 @@ repositories {
 
 dependencies {
     // BouncyCastle: trusted, deterministic Ed25519 (RFC 8032) implementation.
-    api("org.bouncycastle:bcprov-jdk18on:1.78.1")
+    api("org.bouncycastle:bcprov-jdk18on:1.86")
 
     testImplementation(platform("org.junit:junit-bom:5.10.2"))
     testImplementation("org.junit.jupiter:junit-jupiter")
diff --git a/src/main/java/io/vibetensor/attestix/Canonicalizer.java b/src/main/java/io/vibetensor/attestix/Canonicalizer.java
index a595686..49524de 100644
--- a/src/main/java/io/vibetensor/attestix/Canonicalizer.java
+++ b/src/main/java/io/vibetensor/attestix/Canonicalizer.java
@@ -28,7 +28,7 @@
  *
  * <p>Divergence from strict RFC 8785 that callers MUST honour: RFC 8785 does
  * <i>not</i> normalize Unicode, but Attestix applies NFC. Non-whole floats are
- * formatted via Python's {@code repr}, not ECMAScript Ryū - so signed payloads
+ * formatted via Python's {@code repr}, not ECMAScript Ryu - so signed payloads
  * should avoid non-trivial floats. The conformance vectors only use integers and
  * {@code 1.5}, on which all ports agree.
  */
@@ -83,6 +83,9 @@ private static void writeObject(StringBuilder sb, Map<?, ?> map) {
         TreeMap<String, Object> sorted = new TreeMap<>(Canonicalizer::compareByCodePoint);
         for (Map.Entry<?, ?> e : map.entrySet()) {
             String key = nfc(String.valueOf(e.getKey()));
+            if (sorted.containsKey(key)) {
+                throw new IllegalArgumentException("Duplicate normalized object key");
+            }
             sorted.put(key, e.getValue());
         }
         sb.append('{');
@@ -114,7 +117,7 @@ private static void writeArray(StringBuilder sb, List<?> list) {
 
     /**
      * Write a string with NFC normalization and Python {@code json.dumps}-compatible
-     * escaping: only {@code "}, {@code \\}, and the control chars U+0000–U+001F are
+     * escaping: only {@code "}, {@code \\}, and the control chars U+0000-U+001F are
      * escaped (short escapes for b/t/n/f/r, {@code \\uXXXX} otherwise). With
      * {@code ensure_ascii=False}, every other character - including all non-ASCII -
      * is emitted raw (UTF-8 on encode). {@code /} is NOT escaped.
diff --git a/src/main/java/io/vibetensor/attestix/CredentialVerifier.java b/src/main/java/io/vibetensor/attestix/CredentialVerifier.java
index c799574..7eb908d 100644
--- a/src/main/java/io/vibetensor/attestix/CredentialVerifier.java
+++ b/src/main/java/io/vibetensor/attestix/CredentialVerifier.java
@@ -69,9 +69,9 @@ public static VerificationResult verifyCredential(Map<String, Object> vc, byte[]
         }
 
         boolean signatureValid = false;
-        if (proofValue != null) {
-            byte[] canonical = Canonicalizer.canonicalize(signedPayload);
+        if (proofValue != null && issuerPublicKey != null && issuerPublicKey.length == 32) {
             try {
+                byte[] canonical = Canonicalizer.canonicalize(signedPayload);
                 byte[] sig = Base64Url.decode(proofValue);
                 signatureValid = Ed25519.verify(issuerPublicKey, canonical, sig);
             } catch (RuntimeException ex) {
@@ -79,7 +79,7 @@ public static VerificationResult verifyCredential(Map<String, Object> vc, byte[]
             }
         }
 
-        boolean notExpired = checkNotExpired(vc.get("expirationDate"), now);
+        boolean notExpired = !vc.containsKey("expirationDate") || checkNotExpired(vc.get("expirationDate"), now);
         boolean notRevoked = checkNotRevoked(vc.get("credentialStatus"));
 
         return new VerificationResult(signatureValid, notExpired, notRevoked, structureValid);
@@ -88,7 +88,7 @@ public static VerificationResult verifyCredential(Map<String, Object> vc, byte[]
     private static boolean checkNotExpired(Object expirationDate, Instant now) {
         if (!(expirationDate instanceof String) || ((String) expirationDate).isEmpty()) {
             // No expiry => never expires.
-            return true;
+            return false;
         }
         try {
             Instant exp = OffsetDateTime.parse((String) expirationDate).toInstant();
diff --git a/src/test/java/io/vibetensor/attestix/SecurityBoundariesTest.java b/src/test/java/io/vibetensor/attestix/SecurityBoundariesTest.java
new file mode 100644
index 0000000..ad66a91
--- /dev/null
+++ b/src/test/java/io/vibetensor/attestix/SecurityBoundariesTest.java
@@ -0,0 +1,28 @@
+package io.vibetensor.attestix;
+
+import org.junit.jupiter.api.Test;
+import java.time.Instant;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import static org.junit.jupiter.api.Assertions.*;
+
+class SecurityBoundariesTest {
+ @Test void ambiguousNormalizedKeysAreRejected() {
+  Map<String,Object> value = new LinkedHashMap<>();
+  value.put("\u00e9",1); value.put("e\u0301",2);
+  assertThrows(IllegalArgumentException.class, () -> Attestix.canonicalize(value));
+ }
+ @Test void malformedExpiryFailsClosed() {
+  for (Object expiry : new Object[]{null,false,123,"","invalid"}) {
+   Map<String,Object> vc = new LinkedHashMap<>();
+   vc.put("proof",Map.of("proofValue","invalid")); vc.put("expirationDate",expiry);
+   assertFalse(Attestix.verifyCredential(vc,new byte[32],Instant.now()).notExpired());
+  }
+ }
+ @Test void malformedKeyFailsClosed() {
+  assertFalse(Attestix.verifyCredential(Map.of("proof",Map.of("proofValue","AQ==")),new byte[]{1},Instant.now()).verify());
+ }
+ @Test void missingExpiryRemainsUnlimited() {
+  assertTrue(Attestix.verifyCredential(Map.of("proof",Map.of("proofValue","AQ==")),new byte[32],Instant.now()).notExpired());
+ }
+}