diff --git a/src/Keys/AsymmetricPublicKey.php b/src/Keys/AsymmetricPublicKey.php
index 40e72eb..afbcb2d 100644
--- a/src/Keys/AsymmetricPublicKey.php
+++ b/src/Keys/AsymmetricPublicKey.php
@@ -11,9 +11,6 @@
     Util
 };
 use FG\ASN1\Exception\ParserException;
-use Mdanter\Ecc\EccFactory;
-use ParagonIE\EasyECC\EasyECC;
-use ParagonIE\EasyECC\ECDSA\ConstantTimeMath;
 use ParagonIE\EasyECC\ECDSA\PublicKey;
 use ParagonIE\Paseto\Protocol\{
     Version1,
@@ -148,7 +145,7 @@ public static function v4(string $keyMaterial): self
      * @return string
      *
      * @throws TypeError
-     * @throws ParserException
+     * @throws PasetoException
      */
     public function encode(): string
     {
@@ -158,11 +155,15 @@ public function encode(): string
             } elseif (Binary::safeStrlen($this->key) === 98) {
                 Base64UrlSafe::encodeUnpadded(Hex::decode($this->key));
             }
-            return Base64UrlSafe::encodeUnpadded(
-                Hex::decode(
-                    Version3::getPublicKeyCompressed($this->key)
-                )
-            );
+            try {
+                return Base64UrlSafe::encodeUnpadded(
+                    Hex::decode(
+                        Version3::getPublicKeyCompressed($this->key)
+                    )
+                );
+            } catch (ParserException $ex) {
+                throw new PasetoException("ASN.1 Parser Exception", 0, $ex);
+            }
         }
         return Base64UrlSafe::encodeUnpadded($this->key);
     }
diff --git a/src/Parser.php b/src/Parser.php
index ddbae39..b36a6eb 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -19,8 +19,10 @@
     SymmetricKey
 };
 use ParagonIE\ConstantTime\Binary;
-use ParagonIE\Paseto\Parsing\NonExpiringSupport;
-use ParagonIE\Paseto\Parsing\PasetoMessage;
+use ParagonIE\Paseto\Parsing\{
+    NonExpiringSupport,
+    PasetoMessage
+};
 use ParagonIE\Paseto\Rules\NotExpired;
 use ParagonIE\Paseto\Traits\RegisteredClaims;
 use function get_class,
diff --git a/src/Protocol/Version1.php b/src/Protocol/Version1.php
index ad7915f..1d210fd 100644
--- a/src/Protocol/Version1.php
+++ b/src/Protocol/Version1.php
@@ -421,6 +421,7 @@ public static function aeadEncrypt(
             OPENSSL_RAW_DATA,
             Binary::safeSubstr($nonce, 16, 16)
         );
+        Util::wipe($encKey);
         if (!is_string($ciphertext)) {
             throw new PasetoException(
                 'Encryption failed.',
@@ -434,6 +435,7 @@ public static function aeadEncrypt(
             $authKey,
             true
         );
+        Util::wipe($authKey);
 
         // PASETO Version 1 - Encrypt - Step 9:
         return (new PasetoMessage(
@@ -511,8 +513,11 @@ public static function aeadDecrypt(
             $authKey,
             true
         );
+        Util::wipe($authKey);
+
         // PASETO Version 1 - Decrypt - Step 8:
         if (!hash_equals($calc, $mac)) {
+            Util::wipe($encKey);
             throw new SecurityException(
                 'Invalid MAC for given ciphertext.',
                 ExceptionCode::INVALID_MAC
@@ -528,6 +533,7 @@ public static function aeadDecrypt(
             OPENSSL_RAW_DATA,
             Binary::safeSubstr($nonce, 16, 16)
         );
+        Util::wipe($encKey);
         if (!is_string($plaintext)) {
             throw new PasetoException(
                 'Encryption failed.',
diff --git a/src/Protocol/Version3.php b/src/Protocol/Version3.php
index 83913ce..5037711 100644
--- a/src/Protocol/Version3.php
+++ b/src/Protocol/Version3.php
@@ -540,6 +540,7 @@ public static function aeadDecrypt(
 
         // PASETO Version 3 - Decrypt - Step 8:
         if (!hash_equals($calc, $mac)) {
+            Util::wipe($encKey);
             throw new SecurityException(
                 'Invalid MAC for given ciphertext.',
                 ExceptionCode::INVALID_MAC
diff --git a/src/Protocol/Version4.php b/src/Protocol/Version4.php
index 6030464..4677195 100644
--- a/src/Protocol/Version4.php
+++ b/src/Protocol/Version4.php
@@ -405,6 +405,7 @@ public static function aeadEncrypt(
             $nonce2,
             $encKey
         );
+        Util::wipe($encKey);
         if (!is_string($ciphertext)) {
             throw new PasetoException(
                 'Encryption failed.',
@@ -416,7 +417,6 @@ public static function aeadEncrypt(
             Util::preAuthEncode($header, $nonce, $ciphertext, $footer, $implicit),
             $authKey
         );
-        Util::wipe($encKey);
         Util::wipe($authKey);
 
         // PASETO Version 4 - Encrypt - Step 8:
@@ -496,6 +496,7 @@ public static function aeadDecrypt(
             Util::preAuthEncode($header, $nonce, $ciphertext, $footer, $implicit),
             $authKey
         );
+        Util::wipe($authKey);
         // PASETO Version 4 - Decrypt - Step 8:
         if (!hash_equals($calc, $mac)) {
             throw new SecurityException(
@@ -511,6 +512,7 @@ public static function aeadDecrypt(
             $nonce2,
             $encKey
         );
+        Util::wipe($encKey);
         if (!is_string($plaintext)) {
             throw new PasetoException(
                 'Encryption failed.',
diff --git a/src/Purpose.php b/src/Purpose.php
index 0b716c5..76a0e38 100644
--- a/src/Purpose.php
+++ b/src/Purpose.php
@@ -106,7 +106,7 @@ final class Purpose
      *
      * @var array<string, string>
      */
-    private static $sendingKeyToPurpose;
+    private static $sendingKeyToPurpose = [];
 
     /**
      * Inverse of EXPECTED_RECEIVING_KEYS, evaluated and statically cached at
@@ -114,7 +114,7 @@ final class Purpose
      *
      * @var array<string, string>
      */
-    private static $receivingKeyToPurpose;
+    private static $receivingKeyToPurpose = [];
 
     /**
      * @var string
diff --git a/src/ReceivingKeyRing.php b/src/ReceivingKeyRing.php
index db40cab..2843729 100644
--- a/src/ReceivingKeyRing.php
+++ b/src/ReceivingKeyRing.php
@@ -2,8 +2,10 @@
 declare(strict_types=1);
 namespace ParagonIE\Paseto;
 
-use ParagonIE\Paseto\Exception\InvalidKeyException;
-use ParagonIE\Paseto\Exception\PasetoException;
+use ParagonIE\Paseto\Exception\{
+    InvalidKeyException,
+    PasetoException
+};
 use ParagonIE\Paseto\Traits\MultiKeyTrait;
 
 class ReceivingKeyRing implements KeyRingInterface, ReceivingKey
diff --git a/src/Rules/ForAudience.php b/src/Rules/ForAudience.php
index 11fd9f0..ca75aa2 100644
--- a/src/Rules/ForAudience.php
+++ b/src/Rules/ForAudience.php
@@ -18,7 +18,7 @@ class ForAudience implements ValidationRuleInterface
     /** @var string $failure */
     protected $failure = 'OK';
 
-    /** @var string $issuer */
+    /** @var string $audience */
     protected $audience;
 
     /**
diff --git a/src/SendingKeyRing.php b/src/SendingKeyRing.php
index 34af2b0..cd076ba 100644
--- a/src/SendingKeyRing.php
+++ b/src/SendingKeyRing.php
@@ -3,10 +3,14 @@
 namespace ParagonIE\Paseto;
 
 use Exception;
-use ParagonIE\Paseto\Exception\InvalidKeyException;
-use ParagonIE\Paseto\Exception\PasetoException;
-use ParagonIE\Paseto\Keys\AsymmetricSecretKey;
-use ParagonIE\Paseto\Keys\SymmetricKey;
+use ParagonIE\Paseto\Exception\{
+    InvalidKeyException,
+    PasetoException
+};
+use ParagonIE\Paseto\Keys\{
+    AsymmetricSecretKey,
+    SymmetricKey
+};
 use ParagonIE\Paseto\Traits\MultiKeyTrait;
 
 class SendingKeyRing implements KeyRingInterface, SendingKey
diff --git a/src/Util.php b/src/Util.php
index 9b0a9bf..1e90b33 100644
--- a/src/Util.php
+++ b/src/Util.php
@@ -131,7 +131,7 @@ public static function HKDF(
         }
 
         $digest_length = Binary::safeStrlen(
-            hash_hmac($hash, '', '', true)
+            hash($hash, '', true)
         );
 
         // Sanity-check the desired output length.