The unicity distance: An upper bound on the probability of an eavesdropper successfully estimating the secret key

✍ Scribed by A.Kh.Al Jabri

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 420 KB
• Volume: 60
• Category: Article
• ISSN: 0020-0190
• DOI: 10.1016/s0020-0190(96)00138-x

✦ Synopsis

The unicity distance, U, of a secret-key cipher is defined by Shannon as the minimum amount of intercepted ciphertext symbols needed, in principle, to uniquely determine the secret key and, therefore, break the cipher. Accordingly, for a ciphertext of size N symbols less than U, the estimated key will have a nonzero probability of error. Of interest is knowing the chance or probability that an eavesdropper, using the besf estimation rule, successfully estimates the secret key from N ciphertext symbols less than V. An upper bound on this probability is derived in this paper.