code: public final boolean verify(byte[] signature, int offset, int length)
          throws SignatureException {
          if (state == VERIFY) {
              if (signature == null) {
                  throw new IllegalArgumentException("signature is null");
              }
              if (offset < 0 || length < 0) {
                  throw new IllegalArgumentException
                      ("offset or length is less than 0");
              }
              if (signature.length - offset < length) {
                  throw new IllegalArgumentException
                      ("signature too small for specified offset and length");
              }
  
              return engineVerify(signature, offset, length);
          }
          throw new SignatureException("object not initialized for " +
                                       "verification");
      }
docs: Verifies the passed-in signature in the specified array
  of bytes, starting at the specified offset.
  
  <p>A call to this method resets this signature object to the state
  it was in when previously initialized for verification via a
  call to {@code initVerify(PublicKey)}. That is, the object is
  reset and available to verify another signature from the identity
  whose public key was specified in the call to {@code initVerify}.
  
  
  @param signature the signature bytes to be verified.
  @param offset the offset to start from in the array of bytes.
  @param length the number of bytes to use, starting at offset.
  
  @return true if the signature was verified, false if not.
  
  @exception SignatureException if this signature object is not
  initialized properly, the passed-in signature is improperly
  encoded or of the wrong type, if this signature algorithm is unable to
  process the input data provided, etc.
  @exception IllegalArgumentException if the {@code signature}
  byte array is null, or the {@code offset} or {@code length}
  is less than 0, or the sum of the {@code offset} and
  {@code length} is greater than the length of the
  {@code signature} byte array.
  @since 1.4