Variably Modified Permutation Composition: Difference between revisions

Revision as of 18:05, 17 August 2022

Revision as of 23:47, 27 August 2023

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The function was designed such that inverting it, i.e. obtaining {{mono|f}} from {{mono|g}}, would be a complex problem. According to computer simulations the average number of operations required to recover {{mono|f}} from {{mono|g}} for a 16-element permutation is about 2¹¹; for 64-element permutation, about 2⁵³; and for a 256-element permutation, about 2²⁶⁰.{{Citation needed|date=September 2015}}

In 2006 at Cambridge University, Kamil Kulesza investigated the problem of inverting VMPC and concluded "results indicate that VMPC is not a good candidate for a cryptographic one-way function".<ref name="Kulesza2006">{{cite documentweb|last1=Kulesza|first1=Kamil|date= 2008-10-27|title=On Inverting the VMPC One-Way Function|url=http://www-old.newton.ac.uk/preprints/NI06009.pdf|access-date=9 February 2015}}</ref>

The VMPC function is used in an [[encryption]] algorithm – the VMPC [[stream cipher]]. The algorithm allows for efficient in software implementations; to encrypt {{mono|L}} bytes of plaintext do: