Redundancy

Redundancy is an information theoretic measure of the number of bits wasted when transmitting a message.

References

L. R. Knudsen, M. J. B. Robshaw, The Block Cipher Companion. Springer, 2011.
A. Menzes, P. van Oorschot, and S. Vanstone, Handbook of Applied Cryptography. CRC Press, 1996.