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Non-Cyclic Initialization Vector Generation

IP.com Disclosure Number: IPCOM000051143D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Hallett, RJ: AUTHOR

Abstract

This article describes a synchronization algorithm for an output feedback mode (OFM) encryption device which does not allow cycle repetition from its initialization vectors (IVs).

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Non-Cyclic Initialization Vector Generation

This article describes a synchronization algorithm for an output feedback mode (OFM) encryption device which does not allow cycle repetition from its initialization vectors (IVs).

Given a pseudo random number as a seed (IV(1)) and using this value as the initial data and key inputs into an encryption engine, there will be predicted an initialization vector (IV(2)). A certain period or number of iterations (N) exist when feeding the previous initialization vector (IV(i-1)) back into both the data and key inputs of an encryption engine where: IV(1+N = IV(1).

This indicates the beginning of the previous cycle. This period may be long or short, but when it repeats, the strength of any permutations generated from these initialization vectors (IV(N+i)) become weak.

The figure illustrates a system where this effect can be detected, causing the initialization vector to be reseeded, thus eliminating the cyclic characteristics of IV generation.

The time of day (TOD) register 1 is a sequentially increasing counter based on a Unit of time. It is used as the initial seed to the seed register 2 and encryption engine 3. Later, when repetition is detected, the TOD register 1 is also used as a new seed and the new input to the encryption engine 3.

Normally the IV(i-1) register 4 is used as both key and data inputs to the encryption engine 3. However, if the beginning of the previous cycle is detected: IV(i-1) = seed, then the time-of-da...