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History of cryptography and cryptanalysis. Questions that wish to ask about the history of cryptography should use this tag; if you're asking about historical ciphers you may also wish to use the classical-cipher tag.

71 votes

Soft question: Examples where lack of mathematical rigour cause security breaches?

The SSL/TLS protocols have a long and sordid history of informal design, leading to a multitude of attacks: The Bleichenbacher RSAES-PKCS1-v1_5 padding oracle attack, which breaks an RSA-based encryption …
Squeamish Ossifrage's user avatar
13 votes
Accepted

Academic breach revealed too late

In 2004, Xiaoyun Wang's team first publicly reported collisions in MD5, and in 2007, Marc Stevens, Arjen Lenstra, and Benne de Weger reported a chosen-prefix collision attack on MD5. Around the same …
Squeamish Ossifrage's user avatar
10 votes

Soft question: What are examples of beautiful proofs in cryptography?

Theorem. The ECB mode of a block cipher is distinguishable under chosen-plaintext attack with laughably high advantage. Proof.
Squeamish Ossifrage's user avatar
9 votes

Soft question: What are examples of beautiful proofs in cryptography?

Unlike the trivially breakable RSA proposal (paywall-free) that preceded it, Rabin's signature scheme was the first signature scheme in history that still stands under modern scrutiny, provided suitable …
Squeamish Ossifrage's user avatar
5 votes

Turing's (still?) classified inference engine algorithm?

This doesn't answer your question, but you may find clues in two wartime papers of Alan Turing which were formerly classified were declassified and published in the UK National Archives in 2015, and a …
Squeamish Ossifrage's user avatar
5 votes

Academic breach revealed too late

For more information and references, see the Project BULLRUN Dual_EC web site, particularly a detailed chronicle of the background and history until 2015, and the timeline at the Wikipedia article on Dual_EC_DRBG …
Squeamish Ossifrage's user avatar
5 votes
Accepted

Who issued the first SSL certificate?

Spelunking through https://crt.sh, one finds a CA certificate for RSA Data Security, Inc., from 1994, but the oldest certificate it has issued has a validity period starting only on 1998-02-13. That …
Squeamish Ossifrage's user avatar
5 votes

Soft question: What are examples of beautiful proofs in cryptography?

How can you use polynomials evaluation to detect forgery on the internet? Fix a field $k$. Encode a message $m$ as a polynomial $m_1 x^\ell + m_2 x^{\ell - 1} + \cdots + m_\ell x$ of degree $\ell$ in …
Squeamish Ossifrage's user avatar
2 votes

Origin of values for "security margin"?

There is not such a consensus. For example, Salsa20 has a ‘security margin’ of 60%, with 8 out of 20 rounds broken; for ChaCha, it's 65%, with only 7 out of 20 rounds broken. But it is all a heurist …
Squeamish Ossifrage's user avatar
1 vote

Soft question: What are examples of beautiful proofs in cryptography?

How can you expand a short-input pseudorandom function family $F_k\colon \{0,1\}^t \to \{0,1\}^n$ to long inputs? Let $H_r\colon \{0,1\}^* \to \{0,1\}^t$ be a universal hash family with bounded colli …
Squeamish Ossifrage's user avatar