Modes of Operation: ECB Mode

Block ciphers are extremely versatile cryptographic primitives that can provide a large number of different security properties. Determining the way in which a cryptographic primitive is used affects the resulting properties it provides.

One example of using a block cipher in an ‘unconventional’ way (by which we mean a way that doesn’t strictly conform to the basic model of a cryptosystem proposed) is Triple DES. In this case, the block cipher is used in a different way in order to increase the level of security it provides against an exhaustive key search.

We now present several different modes of operation of a block cipher. These are operational rules for a generic block cipher, each of which results in different properties being achieved when they are applied to plaintexts consisting of more than one block. In theory, any block cipher could be used in any of these different modes of operation. The application and the desired properties will, in practice, influence the decision relating to which mode of operation to use.

The first mode of operation is Electronic Code Book (ECB) mode. This mode of operation won’t result in any surprises because ECB mode is simply the terminology for the intuitive way of using a block cipher depicted in the illustration below. The main reason we’ll discuss ECB mode at all is to identify its deficiencies.

Electronic Code Book mode

The first mode of operation is Electronic Code Book (ECB) mode. This mode of operation will not result in any surprises because ECB mode is just terminology for the intuitive way of using a block cipher depicted in the illustration below. The main reason we will discuss ECB mode at all is to identify its deficiencies.