Breaking an Encryption Scheme
It would be easy to break Caesar’s cipher but in general it is hard and in fact exponentially hard as breaking cipher involves some sort of combinatorial (exhaustive) search combined with clever ideas
- such as looking for common English words such as the
Note that encoding/decoding can be computationally expensive but much less so than code breaking
- So as computers get faster, the code breaker’s job gets easier for FIXED coding strategy but much harder for a coding strategy that takes a fixed time
Methods exist for three scenarios
- You only have ciphertext gotten by eavesdropping insecure link
- You have some matched (ciphertext,plaintext) combinations and wish to find plaintext corresponding to some new ciphertext
- You have ability to get ciphertext for any plaintext of your (the code breaker’s) choice