Jailbreaking Proprietary Large Language Models using Word Substitution Cipher

LLMs are aligned to moral and ethical guidelines but remain susceptible to creative prompts called Jailbreak that can bypass the alignment process. However, most jailbreaking prompts contain harmful questions in the natural language (mainly English), which can be detected by the LLM themselves. In this paper, we present jailbreaking prompts encoded using cryptographic techniques. We first present a pilot study on the state-of-the-art LLM, GPT-4, in decoding several safe sentences that have been encrypted using various cryptographic techniques and find that a straightforward word substitution cipher can be decoded most effectively. Motivated by this result, we use this encoding technique for writing jailbreaking prompts. We present a mapping of unsafe words with safe words and ask the unsafe question using these mapped words. Experimental results show an attack success rate (up to 59.42%) of our proposed jailbreaking approach on state-of-the-art proprietary models including ChatGPT, GPT-4, and Gemini-Pro. Additionally, we discuss the over-defensiveness of these models. We believe that our work will encourage further research in making these LLMs more robust while maintaining their decoding capabilities.