An Overview of Cryptography

"This scheme also provides nonrepudiation since it proves that Alice sent the message; if the hash value recovered by Bob using Alice's public key proves that the message has not been altered, then only Alice could have created the digital signature."

This is a common misconception.

Just because a signature verifies under Alice's public key, it does not necessarily imply Alice generated the signature. For many common signature schemes, if Bob makes a signature using their public/private key, Alice can produce a different private/public key such that Bob's signature will verify under Alice's key.

Paper (we) wrote on the impacts of this: https://eprint.iacr.org/2019/779

I may be misunderstanding the author's use of terms here, but this seems wrong (section 3.1):

> A block cipher is so-called because the scheme encrypts one block of data at a time using the same key on each block. In general, the same plaintext block will always encrypt to the same ciphertext when using the same key in a block cipher whereas the same plaintext will encrypt to different ciphertext in a stream cipher.

A block cipher will turn the same plaintext into the same ciphertext only if you're using it with the ECB mode; otherwise, the same plaintext in different places with the same key will encrypt into different ciphertext.

If he means "key" in the sense of "final thing that gets XORed to make the ciphertext", then that's true, but then it's equally true of stream ciphers as well.

Cryptography was both my favorite topic in school and the one that cemented my realization in that I wasn't good enough to do math for a living.

Shameless plug: I’ve been writing my own introduction for students/developers/consultants/... and you can read it online for free it seems (or at least some chapters): https://www.manning.com/books/real-world-cryptography

Side note: Diffie-Hellman predates RSA. I attended a talk by Rivest once, where he vividly described how that paper triggered them into exploring whether public key crypto was really possible or not. They ended up constructing RSA from those sessions.

"In many of the descriptions below, two communicating parties will be referred to as Alice and Bob; this is the common nomenclature in the crypto field and literature to make it easier to identify the communicating parties. If there is a third and fourth party to the communication, they will be referred to as Carol and Dave, respectively. A malicious party is referred to as Mallory, an eavesdropper as Eve, and a trusted third party as Trent."

I really love this naming system.

Holy smokes - I 'ran' into this website a few weeks ago whilst cleaning up an old computer.... and chuckled (my copy that I had saved on this computer is/was old - lets just say that).

And then I chance upon it being talked about on HN. Small world and maybe the universe is telling me something ;-)

For those who want a conceptual, visual, cartoon explainer, check out our 1min animated series: https://gun.eco/docs/Cartoon-Cryptography

I strongly recommend “The Code Book” by Simon Singh. Really readable and very informative!

Great paper! Given the write-ups of old and broken crypto, perhaps a better title would be History of Cryptography?

Very interesting paper indeed.

Could be more appealing if the vanilla html was properly styled though.

This is such an awesome paper, thanks for posting it!