code: public OmemoFingerprint getFingerprint(OmemoDevice userDevice)
              throws CorruptedOmemoKeyException {
  
          T_IdKeyPair keyPair = loadOmemoIdentityKeyPair(userDevice);
          if (keyPair == null) {
              return null;
          }
  
          return keyUtil().getFingerprintOfIdentityKey(keyUtil().identityKeyFromPair(keyPair));
      }
docs: Return our identityKeys fingerprint.
  
  @param userDevice our OmemoDevice.
  @return fingerprint of our identityKeyPair
  
  @throws CorruptedOmemoKeyException if the identityKey of userDevice is corrupted.