Secret Sharing Scheme Using Natural Language Text

摘要

Modifying the idea of the visual cryptography, we propose a method of sharing a secret key using natural language texts. Our target here is restricted to Japanese texts. Each participant obtains a share, which is a Japanese text in our scheme. When a certain number of participants retrieve the secret key, they supply their shares and pile up these natural language texts. The sequence of the first, second (and so on) letters occurred in the pile shows the secret text. The order of the pile is significant, and changing the order may yield the distinct secret text. It is easy to pile the shared natural language texts by computer operation. Human eyes can recognize the secret text from the piled texts, however, we aim to construct a natural language text secret sharing scheme employing a morphological analyzer because a meaningless phrase is a chain of morphemes consisting of one word with a high probability. We can make a shared natural text look like a natural text without any secret meaning by synthesizing using a text database.