Remove identifiers from ScannableFingerprint

Although it helps to eliminate confusion when people inadvertantly
scan the wrong code, people might share the QR code image publicly
and inadvertantly publish their identifier.

// FREEBIE

Author: moxie0

java/src/main/java/org/whispersystems/libsignal/fingerprint/BaseFingerprintType.java

@@ -5,79 +5,34 @@
  */
 package org.whispersystems.libsignal.fingerprint;
 
-import org.whispersystems.libsignal.IdentityKey;
 import org.whispersystems.libsignal.util.ByteUtil;
-import org.whispersystems.libsignal.util.IdentityKeyComparator;
 
-import java.io.ByteArrayOutputStream;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.LinkedList;
-import java.util.List;
+public class DisplayableFingerprint {
 
-public class DisplayableFingerprint extends BaseFingerprintType {
+  private final String localFingerprintNumbers;
+  private final String remoteFingerprintNumbers;
 
-  private static final int VERSION = 0;
-
-  private final String localFingerprint;
-  private final String remoteFingerprint;
-
-  DisplayableFingerprint(int iterations,
-                         String localStableIdentifier, final IdentityKey localIdentityKey,
-                         String remoteStableIdentifier, final IdentityKey remoteIdentityKey)
-  {
-    this(iterations, localStableIdentifier,
-         new LinkedList<IdentityKey>(){{
-           add(localIdentityKey);
-         }},
-         remoteStableIdentifier,
-         new LinkedList<IdentityKey>() {{
-           add(remoteIdentityKey);
-         }});
-  }
-
-  DisplayableFingerprint(int iterations,
-                         String localStableIdentifier, List<IdentityKey> localIdentityKeys,
-                         String remoteStableIdentifier, List<IdentityKey> remoteIdentityKeys)
+  DisplayableFingerprint(byte[] localFingerprint, byte[] remoteFingerprint)
   {
-    this.localFingerprint  = getDisplayStringFor(iterations, localStableIdentifier, localIdentityKeys);
-    this.remoteFingerprint = getDisplayStringFor(iterations, remoteStableIdentifier, remoteIdentityKeys);
+    this.localFingerprintNumbers  = getDisplayStringFor(localFingerprint);
+    this.remoteFingerprintNumbers = getDisplayStringFor(remoteFingerprint);
   }
 
   public String getDisplayText() {
-    if (localFingerprint.compareTo(remoteFingerprint) <= 0) {
-      return localFingerprint + remoteFingerprint;
+    if (localFingerprintNumbers.compareTo(remoteFingerprintNumbers) <= 0) {
+      return localFingerprintNumbers + remoteFingerprintNumbers;
     } else {
-      return remoteFingerprint + localFingerprint;
+      return remoteFingerprintNumbers + localFingerprintNumbers;
     }
   }
 
-  private String getDisplayStringFor(int iterations, String stableIdentifier, List<IdentityKey> unsortedIdentityKeys) {
-    try {
-      ArrayList<IdentityKey> sortedIdentityKeys = new ArrayList<>(unsortedIdentityKeys);
-      Collections.sort(sortedIdentityKeys, new IdentityKeyComparator());
-
-      MessageDigest digest    = MessageDigest.getInstance("SHA-512");
-      byte[]        publicKey = getLogicalKeyBytes(sortedIdentityKeys);
-      byte[]        hash      = ByteUtil.combine(ByteUtil.shortToByteArray(VERSION),
-                                                 publicKey, stableIdentifier.getBytes());
-
-      for (int i=0;i<iterations;i++) {
-        digest.update(hash);
-        hash = digest.digest(publicKey);
-      }
-
-      return getEncodedChunk(hash, 0) +
-          getEncodedChunk(hash, 5) +
-          getEncodedChunk(hash, 10) +
-          getEncodedChunk(hash, 15) +
-          getEncodedChunk(hash, 20) +
-          getEncodedChunk(hash, 25);
-    } catch (NoSuchAlgorithmException e) {
-      throw new AssertionError(e);
-    }
+  private String getDisplayStringFor(byte[] fingerprint) {
+    return getEncodedChunk(fingerprint, 0)  +
+           getEncodedChunk(fingerprint, 5)  +
+           getEncodedChunk(fingerprint, 10) +
+           getEncodedChunk(fingerprint, 15) +
+           getEncodedChunk(fingerprint, 20) +
+           getEncodedChunk(fingerprint, 25);
   }
 
   private String getEncodedChunk(byte[] hash, int offset) {