In Chapter 6, Question 6.8, of his book “Cryptography and Network Security Principles and Practices”, William Stalling asks:
Why do some block cipher modes of operation only use encryption while others use both encryption and decryption?
ECB and CBC use encryption function and decryption function while CFB, OFB and CTR use encryption function for decryption as well. What is the logic behind it? Is it because ECB and CBC generates output of Block Cipher type – while CFB, OFB and CTR generates output of Stream Cipher type?