A very lightweight encryption method based on multiple substitution tables

We present a very lightweight encryption method based on multiple substitution tables. The method does not use sophisticated integer arithmetic and is therefore suitable for small embedded systems and other applications using simple processing elements. Plain text is encrypted one byte at a time. Each byte is replaced by the substitution element in the current table, and the plain text byte also determines the table to be used for the next byte. Encrypting and decrypting one byte involves only a table look-up, no arithmetic or bit manipulation. The same plain text byte has very small probability of being encrypted the same way twice in a row. We also present additional techniques for making the method secure against attacks when used in applications where the messages may have special or restricted forms.