The Monographic Substitution Cipher: From Julius Caesar to the KGB - Comments

[bapowell]

bapowell submitted a new PF Insights post

The Monographic Substitution Cipher: From Julius Caesar to the KGB

Continue reading the Original PF Insights Post.

 

[Greg Bernhardt]

Superb Insight!

 

[anorlunda]

Well done, I learned a lot. Thank you for the education.

It might be worthwhile to mention that good encryption practice would be to keep the message as short as possible to make statistical analysis more difficult. In the extreme, shortened plaintext morphs into code and encryption becomes unnecessary.

 

[Lord Crc]

It might be worthwhile to mention that good encryption practice would be to keep the message as short as possible to make statistical analysis more difficult. In the extreme, shortened plaintext morphs into code and encryption becomes unnecessary.

On the other hand, if an attacker can control parts of the plaintext, compression can leak information as explained here: http://security.stackexchange.com/a/19914

 

[anorlunda]

n the other hand, if an attacker can control parts of the plaintext, compression can leak information as explained here: http://security.stackexchange.com/a/19914

I didn't have compression in mind. Nevertheless, the tactic you mention is clever. I'm reminded of the old "Spy Versus Spy" cartoons from Mad Magazine.

 

[Lord Crc]

I didn't have compression in mind.

But your scheme is a form of compression, since the encoded text gets shorter.

Anyway, just wanted to point out that getting encryption right is hard, so many things one have to consider.

And yes, the various side channels and so on they manage to exploit is impressive and does indeed feel like Spy vs Spy :)

 

[anorlunda]

if an attacker can control parts of the plaintext

I just remembered the canonical example of that, Heil Hitler.

 

[nsaspook]

Chosen-plain/ciphertext attacks and hardware side channels are the bacon and eggs of Cryptanalysis.

In addition to mathematical analysis of cryptographic algorithms, cryptanalysis includes the study of side-channel attacks that do not target weaknesses in the cryptographic algorithms themselves, but instead exploit weaknesses in their implementation.