We introduce a new methodology for designing block ciphers with provable security against differential and linear cryptanalysis. It is based on three new principles: change of the location of round functions, round functions with recursive structure, and substitution boxes of different sizes. The first realizes parallel computation of the round functions without losing provable security, and th...

The authors discuss what is provable security in cryptography. Think that provable security is asymptotic, relative, and dynamic, and only a supplement to but not a replacement of exact security analysis. Because the conjecture P ≠ NP has not been proven yet, and it is possible in terms of the two incompleteness theorems of Kurt Gödel that there is some cryptosystem of which the security cannot...

The most common method used for user security is textual passwords. But they are vulnerable to eves dropping, dictionary attack, shoulder surfing etc. To address this problem, text can be combined with colors to generate session passwords called hybrid textual authentication for authentication in multi – cloud. Provable data possession is a technique for ensuring data integrity. We present a co...

In 2007, the US National Institute for Standards and Technology announced a call for the design of a new cryptographic hash algorithm in response to the vulnerabilities identified in widely employed hash functions, such as MD5 and SHA-1. NIST received many submissions, 51 of which got accepted to the first round. At present, 5 candidates are left in the third round of the competition. An import...