def crack(ciphertext, iv):
    result = b''
    for b in range(0, len(ciphertext), block_size):
        block = ciphertext[b:b+block_size]
        previous_block = ciphertext[b-block_size:b] if b != 0 else iv
        suffix = b''
        for i in range(block_size):
            for byte in range(1, 256):
                padding = xor_bytes(suffix, bytes(len(suffix) * [i+1]))
                xor_block = bytes([0] * (block_size - len(padding) - 1)) + bytes([byte]) + padding
                if padding_oracle(block, xor_bytes(previous_block, xor_block)):
                    suffix = bytes([(i+1) ^ byte]) + suffix
                    break
            else:
                suffix = bytes([i+1]) + suffix
        result += suffix
    return unpad(result)