Introduction to simple ciphers
Although they are frequently criticized for their lack of sophistication, simple ciphers provide numerous benefits for malware:
- They are sufficiently compact, which means they can function in environments with limited space, such as exploited shell code
- They lack the overt visibility associated with more intricate ciphers
- Due to their minimal overhead, they have minimal effect on performance
In this section, we will look at some simple ciphers and show their application in malware development.
Caesar cipher
One of the earliest encryption methods to be employed is the Caesar cipher. Originating during the time of the Roman empire, the Caesar cipher concealed messages that were conveyed across battlefields by couriers. This uncomplicated cipher involves shifting the letters of the alphabet by three positions to the right. Each character that’s exchanged for an alternative character in the ciphertext defines a substitution...