Add FingerprintUtil.keyIdFromFingerprint()

Author: vanitasvitae

pg/src/main/java/org/bouncycastle/bcpg/FingerprintUtil.java

@@ -6,6 +6,30 @@
 public class FingerprintUtil
 {
 
+    /**
+     * Derive a key-id from the given key fingerprint.
+     * This method can derive key-ids from v4, v5 (LibrePGP) and v6 keys.
+     * For keys with other versions (2,3) it will return 0.
+     *
+     * @param keyVersion version of the key
+     * @param fingerprint fingerprint of the key
+     * @return derived key-id
+     */
+    public static long keyIdFromFingerprint(int keyVersion, byte[] fingerprint)
+    {
+        switch (keyVersion)
+        {
+            case PublicKeyPacket.VERSION_4:
+                return keyIdFromV4Fingerprint(fingerprint);
+            case 5:
+                return keyIdFromLibrePgpFingerprint(fingerprint);
+            case PublicKeyPacket.VERSION_6:
+                return keyIdFromV6Fingerprint(fingerprint);
+            default:
+                return 0;
+        }
+    }
+
     /**
      * Derive a 64 bit key-id from a version 6 OpenPGP fingerprint.
      * For v6 keys, the key-id corresponds to the left-most 8 octets of the fingerprint.

pg/src/test/java/org/bouncycastle/bcpg/test/FingerprintUtilTest.java

@@ -47,6 +47,19 @@ private void testLibrePgpKeyIdFromFingerprint()
             -3812177997909612905L, FingerprintUtil.keyIdFromLibrePgpFingerprint(decoded));
     }
 
+    private void testKeyIdFromFingerprint()
+    {
+        isEquals("v4 key-id from fingerprint mismatch",
+                -5425419407118114754L, FingerprintUtil.keyIdFromFingerprint(
+                        4, Hex.decode("1D018C772DF8C5EF86A1DCC9B4B509CB5936E03E")));
+        isEquals("v5 key-id from fingerprint mismatch",
+                -3812177997909612905L, FingerprintUtil.keyIdFromFingerprint(
+                        5, Hex.decode("cb186c4f0609a697e4d52dfa6c722b0c1f1e27c18a56708f6525ec27bad9acc9")));
+        isEquals("v6 key-id from fingerprint mismatch",
+                -3812177997909612905L, FingerprintUtil.keyIdFromFingerprint(
+                        6, Hex.decode("cb186c4f0609a697e4d52dfa6c722b0c1f1e27c18a56708f6525ec27bad9acc9")));
+    }
+
     private void testLeftMostEqualsRightMostFor8Bytes()
     {
         byte[] bytes = new byte[] {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08};
@@ -95,6 +108,7 @@ public void performTest()
         testLibrePgpKeyIdFromFingerprint();
         testLeftMostEqualsRightMostFor8Bytes();
         testWriteKeyIdToBytes();
+        testKeyIdFromFingerprint();
     }
 
     public static void main(String[] args)