rephrase OKP subtypes concepts

Author: edudobay

src/JWK.php

@@ -31,9 +31,10 @@ class JWK
         // 'P-521' => '1.3.132.0.35', // Len: 132 (not supported)
     ];
 
-    // 'crv' identifier => JWT 'alg'
-    private const OKP_CURVES = [
-        'Ed25519' => 'EdDSA',
+    // For keys with "kty" equal to "OKP" (Octet Key Pair), the "crv" parameter must contain the key subtype.
+    // This library supports the following subtypes:
+    private const OKP_SUBTYPES = [
+        'Ed25519' => true, // RFC 8037
     ];
 
     /**
@@ -160,17 +161,17 @@ public static function parseKey(array $jwk, string $defaultAlg = null): ?Key
                     throw new UnexpectedValueException('crv not set');
                 }
 
-                if (!isset(self::OKP_CURVES[$jwk['crv']])) {
-                    throw new DomainException('Unrecognised or unsupported OKP curve');
+                if (empty(self::OKP_SUBTYPES[$jwk['crv']])) {
+                    throw new DomainException('Unrecognised or unsupported OKP key subtype');
                 }
 
                 if (empty($jwk['x'])) {
                     throw new UnexpectedValueException('x not set');
                 }
 
+                // This library works internally with EdDSA keys (Ed25519) encoded in standard base64.
                 $publicKey = JWT::convertBase64urlToBase64($jwk['x']);
-                $alg = self::OKP_CURVES[$jwk['crv']];
-                return new Key($publicKey, $alg);
+                return new Key($publicKey, $jwk['alg']);
             default:
                 break;
         }