# Questions tagged [history]

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.

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### What were Alan Turing and their team searching before doing KPA in the movie "The imitation game"?

I just watched the movie "The imitation game" (2014) which is based on Alan Turing's biography. At some point in the movie the machine built by Turing wasn't fast enough to decrypt the ...
54 views

### Early field use of digital signature

What are documented early field uses of digital signature? The oldest I found is reported by Charles H. Bennett, Gilles Brassard, Seth Breidbart, Stephen Wiesner's Quantum Cryptography, or Unforgeable ...
3k views

### Common Classical Ciphers

When studying cryptography, the first thing every student learns is some historical ciphers. There are way too many of those ciphers to name them all. So my question is: What are the most important ...
1k views

A few years ago, I've heard about a harsh report from an American institution (I've forgotten which one, but it was something like the NSA) about IACR conferences. Which report could it be? I think ...
284 views

### Notable Non-Western Cryptosystems that have been widely deployed?

I was recently watching Sneakers (which Len Adleman advised on their "cryptography" sub-plot), which included a line along the lines of: [Some hardware that ostensibly breaks American ...
288 views

### Examples of Weak Cryptography being exploited in the wild by cybercriminals?

As a theorist, I often motivate the need for strong cryptography via simplistic methods, such as "If this did not exist, your online bank transactions would be vulnerable". This is of course ...
50 views

### Did the formalization of PKCS#1 RSA key formats come before or after X.509?

The paper introducing the RSA cryptosystem titled "A Method for Obtaining Digital Signature and Public-Key Cryptosystems" was published in 1978. The initial version of X.500 published by ...
58 views

### Where is the "Letter to NBS, October 22, 1975"

Discussions of the weakness of the U.S. Data Encryption Standard frequently cite a letter by Martin Hellman and Whitfield Diffie to the National Bureau of Standards that reported stated: Whit Diffie ...
99 views

### In my opinion a lot of encryption paper have small contribution in terms of security improvements [closed]

I used to saw a lot of encryption papers that have small significance in security improvements especially in terms of entropy, histogram and coefficient correlation especially in image encryption. Why ...
90 views

### What are the fundamental roots of modern symmetric encryption?

In academic pursuits, we often have people (and their ideas) who are considered fundamental to the subject, such as Bayes and probability. In cryptography, it's obvious to see that the Diffie-Hellman ...
230 views

### Would asymmetric cryptography be feasible in World War II?

Assuming people in the forties would have known asymmetric cryptographic methods like RSA, would they have been able to make sensible use of them? There were no real electronic computers at the time, ...
101 views

### Why was it easier to decode messages that you had several copies of?

During WW1 the German ambassador in Washington, von Bernstorff, blamed their numerous transmissions of the same messages as the cause for the successful decoding done by the British. I don't see the ...
405 views

### How were codes in WW1 reciphered (to enhance security levels) without them turning meaningless?

In WW1, the Germans made their communications secret by encoding their messages. This meant that the message's sender would have a codebook with all possible words and phrases he might use listed in ...
876 views

### Crypto AG (Switzerland) - Which algorithms were used and how did the backdoors work?

Backstory Crypto AG was a company located in Switzerland that specialized in communication security. They produced a number of encryption machines (some similar to the infamous Enigma) used for ...
245 views

### Security properties of ElGamal encryption variants

I'll use Taher ElGamal's A Public Key Cryptosystem and a Signature Scheme Based on Discrete Logarithms (July 1985 in IEEE Transactions on Information Theory, formerly in proceedings of Crypto 1984) as ...
92 views

### Side-channel attack in the real wold [duplicate]

I have a big problem to figure how the security model in papers about side-channel are relevant (briefly the attacker has a partial access to the hardware). Why these breaches are so seriously ...
50 views

### Are there official test vectors for historic ciphers? [closed]

In many cases when cryptographic algorithms are published the paper also provides a set of test vectors that can be used by developers to verify their implementations. For historic ciphers such as ...
391 views

### Academic breach revealed too late

Do you know if is has already happened (since 1980), that someone (academic or not) has "broken" (even in a weak sense) some cryptographic assumption, but has chosen to not first publish and directly ...
160 views

### Could public-key crypto be performed long ago if the idea had been discovered?

Public-key cryptography was not invented until the 1970's. Apart from the idea not existing earlier (as talked about here), is there any reason it could not have been used earlier? For example, are ...
339 views

### Most secure but feasible encryption running on WWII technology

Imagine you are transported back to ~1940. What is the best (i.e. most secure, but technologically feasible) encryption you can think of for widespread (i.e. military) use? How would you implement it?
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### What was used for symmetric message authentication before HMAC was invented?

Currently, Carter Wegman MACs are popular. Before that, HMAC was popular. What was popular before HMAC? Was it CBC-MAC? Something else? I know about NIST FIPS 113 "Data Authentication Algorithm" ...
790 views

### Soft question: What are examples of beautiful proofs in cryptography? [closed]

These may include any proofs, reductions, constructions, etc. For example, simple solutions to problems which at first sight seem difficult. Elegant construction that hide deep mathematical concepts, ...
9k views

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

Cryptographic tools can often become adopted even when their security proofs lack mathematical rigour - or altogether missing. Are there famous cases of security breaches in the industry, where the ...
115 views

### What is the "brand X" cipher mentioned in the Usenet thread about RC4?

In the original Usenet thread about RC4 when it was finally reverse engineered, a user by the name of Michael Johnson mentioned that the RC4 algorithm looked surprisingly like another proprietary ...
222 views

### Why did Rabin use $x(x + b)$ instead of just $x^2$ in the original paper?

Encryption in the original Rabin scheme took a message $x$ and computed $x(x + b) \bmod n$, where $0 \le b \lt n$ and $n$ is the product of two secret primes $p$ and $q$. The private key is defined as ...
300 views

### What is the origin of the phrase "Don't roll your own crypto"?

The phrase is well-known and widely used, it is often attributed to Bruce Schneier and is indeed relevant to his Schneier's Law. However, I wasn't able to find this specific wording among Schneier's ...
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### Difference in SKIPJACK algorithms

This is going back a ways... Schneier discusses SKIPJACK at Declassifying Skipjack. Schneier offers a link to a reference implementation at ftp://ftp.funet.fi/pub/crypt/cryptography/symmetric/skipjack ...
171 views

### Origin of values for "security margin"?

It seems that the acceptable "security margin" for ciphers is set to be between 25% and 30% as a target by designers, where this number represents the number of rounds that remain "unbroken" for a ...
203 views

### When was hash chain first used?

Hash linking is used to prove the integrity of a blockchain, or similar systems. When was that technique first used? I would guess it was early, maybe 1950s/1960s?
2k views

### 80-bit collision resistance because of 80-bit x87 registers?

This is just a curious question, and it probably doesn't belong here anyway, and I'm just being bold asking it here. 80-bit used to be considered an adequate level of security, Skipjack and SHA1 ...
331 views

### How was the 5 digit random number in the VIC cipher generated?

Knowing that VIC was a "spy cipher" it is unlikely that the agents used a cryptographic device to genreate the 5 digit number but how did they do it?
806 views

### Why did MD4 replace MD2?

MD2 was a hash function based on swapping bytes in a state array permutation, much like the RC4 stream cipher, whereas MD4 was a novel construction. MD4 replaced MD2 despite the fact that MD4 is more ...
826 views

### What motivated the creation of RSA and ECDH?

Recently I've been learning about cryptography and so far I am loving it. However, there are some things I do not comprehend. As far as I know, RSA was published in 1979 while New Directions on ...
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### Old French Cipher w/ Text Hidden In Drawing

I'm trying to find a cipher challenge I saw a few years back, it was an old drawing (I think 1800's or earlier) with clouds and stars on it and French text was hidden in the image. Does anyone happen ...
1k views

### In the RSA DES challenges, how did the contestants know they had found the right key considering they weren't given any plaintext?

If the contestants were given both the plaintext and ciphertext, it's straightforward. Just bruteforce all 56-bit keys until you find one that maps the given plaintext to the given ciphertext. But ...
183 views

### Enigma: a Question from WW2

I have seen in the Imitation Game that the Germans reset the Enigma at midnight sharp, and then they start messaging by sending the weather report in the morning. But the device made by Alan Turing, ...
903 views

### Is RSA inspired by Diffie Hellman?

I read a bit of A Method for Obtaining Digital Signatures and Public-Key Cryptosystems that introduced RSA in 1977, and, while learning the steps in RSA a few days ago, I noticed that they are similar ...
492 views

### Who said "32 round Rijndael" in the third AES Conference

This is a historical question. In the third AES Conference of NIST (AES3), April 13-14, 2000, New York, near the end of the conference, one representative for each of the last 5 candidates sit on a ...
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### Cryptanalysis in the middle ages -- publications

Are there any publications, articles or literature discussing cryptanalysis and crypt breaking techniques in the middle-ages? I have seen various manuals from the middle ages describing various types ...
2k views

### Where can I find a description of the SHA-0 hash algorithm?

Where can I find the description and or pseudocode for the SHA-0 hash algorithm? I am looking for something on these lines: HMAC RIPEMD. I have been implementing a few of those (HMAC, HOTP, TOTP and ...
769 views

### What was the BassOmatic cipher, and what made it so weak?

According to Wikipedia, this homebrew cipher was originally used in PGP, before Phil Zimmermann replaced it with IDEA. Supposedly, insecurities in the algorithm were pointed out to him, leading to ...
582 views

### ECDSA public key recovery is discovered by whom?

I'm looking for the history of the method (ECDSA public key recovery from signature). Where did this implementation first appear in (is it bitcoin?) and who discovered this method?
280 views

### Aside from DES, has the NSA ever strengthened algorithms?

When DES was originally developed, the NSA changed the s-boxes. For decades, people thought that their changes introduced a backdoor, but then it was discovered that their changes actually ...
11k views

### How come Public key cryptography wasn't discovered earlier?

I became interested in crypto lately and read about symmetric and public key crypto algorithms. I understand how crucial the discoveries of the 1970s like RSA, DES and DH were in advancing the ...
59 views

### Would it be possible to negotiate a key of 128 or 256 bits strength using Merkle puzzles?

One can be fascinated by the simplicity of the schemes created by Ralf Merkle; like the Merkle tree or his key negociation protocol over an insecure channel. Wikipedia has some material on "Merkle ...
188 views

### Why is XOR preferred over XNOR in cryptography? [duplicate]

The advantages and properties exhibited by XOR are also exhibited by XNOR, like the ones mentioned in many answers like this one Information is preserved. $c = a \oplus b$. One may recover \$a = c \...
5k views

### Why did Histiaeus tattoo his slave's head?

The story is often told that Histiaeus tattooed a secret message on his slave's head, waited for his hair to grow back, then sent him off to Miletus. Why would he have done this? The story is usually ...
3k views

### What was the first hash and what problem was it supposed to solve?

Today's hashes have many uses. File integrity, verification of a secret without revealing the secret (i.e. passwords), hash maps, bloom filters, and probably a few more cases not immediately coming to ...