A STATISTICAL ANALYSIS OF SOME STANDARD CIPHERS’ CRYPTOGRAPHIC PRIMITIVES

Abstract

Encryption is ubiquitous in the modern environment. While public/private key architecture has provided an amazing and powerful way to encrypt information so that only one intended recipient can decrypt, the computation required for this approach means that this encryption method can quickly grow extremely expensive. With that in mind, there are a variety of open-source stream ciphers that seek to provide relatively inexpensive stream ciphers to securely encrypt information. But these stream ciphers all operate using very different techniques to generate their keystream, as seen in the stark differences in paradigms between ciphers. As such, it is not immediately clear what operations are required to achieve the desired level of encryption. What cryptographic primitives are most common or efficacious in achieving security? Examining the Data Encryption Standard, Advanced Encryption Standard, and the stream cipher winners of the eStream II competition, an underlying trend composed of two operations emerges. Despite observing no clear n-grams defining precise cryptographic primitives, we identify a general structure common to all stream ciphers. Additionally, we identify that substitution boxes or multiplication operations are not necessary for stream ciphers, whereas addition and rotation operations seem to be essential.