0
votes
0answers
2 views

Are there some well-known crypto APIs that leak information?

Are there any well-known crypto APIs or libraries that leak or used to leak information (it can be the key or anything else)?
0
votes
1answer
15 views

Calculating 3DES Key Check Value (KCV)

I am trying to verify a Triple DES Key Component generated by PC Crypto. The key portion is: E6F1081FEA4C402CC192B65DE367EC3E and the KCV value that should be ...
3
votes
2answers
24 views

Order-Preserving Encryption (OPE) and leakage

I recently came across OPE and Order-Revealing Encryption (ORE), but I didn't exactly got the idea why they are important. What's exactly important about them? Are they actually used in practice? My ...
3
votes
0answers
16 views

SAT-Based Public Key Cryptosystem

I am researching post quantum cryptography and I've stumbled upon this article which presents a PKC with an np-complete (SAT) trapdoor. I was wondering if someone could help me understand the way the ...
1
vote
3answers
52 views

Is this an effective obfuscation technique?

Long ago I created a simple program which obfuscated a file by taking the first byte, then XORing it with the second, taking the (original) 2nd byte and X-ORing with the 3rd, etc, down the line. The ...
12
votes
2answers
2k views

Can Shannon's entropy be used to determine if a file is encrypted?

If we have to determine a file is encrypted or not, can we use Shannon's entropy algorithm on the file? As discussed here, the entropy (in bits per byte) being closer to 0 is considered as more ...
0
votes
2answers
78 views

Can a hash have more than one input?

From a definition stand point, can a hashing algorithm have more than one input, ex: $H(m_1, m_2, m_3)$? If not why are algorithms like bcrypt, scrypt and pbkdf2 referred to as password hashing ...
2
votes
2answers
17 views

HSM RNG - Compliance to FIPS 186-2

If the RNG of a HSM is said to be compliant to FIPS 140-2 (approved DRBG - SP 800-90 CTR mode) does also imply that it is compliant to FIPS 186-2 ?
2
votes
2answers
108 views

If I send a signed email, how does the end user get the public key?

I am sending a signed email using Python and smtplib. I have successfully signed the email using this example: http://proj.badc.rl.ac.uk/svn/ndg-security/branches/Dependencies/m2crypto/doc/howto.smime....
1
vote
1answer
38 views

How to meter and limit number of files encrypted?

First my apologies if this isn't the right forum for this but here's my problem : I have a black box that takes an input file and produces an output file. I want to sell this black box to a customer ...
0
votes
1answer
32 views

In which situation is HMAC mandatory rather than signature?

I’ve seen that the question has been asked already but this is still confusing to me. In a digital signature, Alice sends a message M and the ...
2
votes
1answer
60 views

If I encrypt data with two different ECC Private keys, how secure is the result?

I'm wondering whether encrypting data with two different 256-bit ECC keys will result in a more secure encryption (minimum 384 bit equivalent) or will result in data that's effectively encrypted with ...
1
vote
1answer
37 views

Encoding an element in $r=r'||h(r')$ way

We consider a finite field $\mathbb{F}_p$, where $p$ is a large prime e.g. 256-bit. We have $b$ a fixed element of the field. We encode it as $b'=b||h(b)$, where $h(.)$ is a cryptographic hash ...
24
votes
2answers
8k views

What is entropy?

We discuss a lot of topics and use measures of entropy to determine how difficult it is for an attacker to be successful. What does entropy mean in the context of cryptography? How is entropy ...
0
votes
0answers
15 views

Homomorphic encryption implementation over circuits or assembly code [on hold]

I've looked at a few implementation of homomorphic encryption, such as HElib, but they only consider additions/multiplications and such. Is anyone aware of any implementation of homomorphic ...
0
votes
0answers
9 views

Entropy of Hash function [duplicate]

How is the entropy of the output of hash functions are defined? More specifically I saw in the paper https://eprint.iacr.org/2013/383.pdf Table 3 page 24. The entropy of challenge is mentioned which ...
12
votes
4answers
3k views

Which public key cryptosystems are not based on number theory?

Are there any public key cryptographic systems whose hardness assumptions don't involve number theoretic problems?
2
votes
1answer
166 views

Security of basic SHA256 MAC in an authenticate-then-encrypt scheme

I know the following construct is insecure if the MAC as defined below is appended to the encrypted message in an Encrypt then Authenticate (EtA) scheme. $k_1$: encryption key $k_2$: authentication ...
3
votes
1answer
129 views

RSA: special parameters construction

I have to show that the following construction of $q$ allows to factorize $N$ : $p \in \mathbb{P}$, the set of primes $q \gets p \cdot \left((p - 1)^{-1} \bmod e\right) \bmod e$ $k=1$ while $q \not \...
3
votes
1answer
26 views

Proof for collision resistance on a block-based hash

I am designing an unkeyed hash based on the SIMON cipher. This is a follow up to “this” question. A quick summary: I have an ECC engine and the SIMON cipher in hardware, and it’s in an extremely ...
3
votes
1answer
44 views

What do the last chunks of the output string of Scrypt contain?

When you use scrypt to hash a string, it will generate something like: ...
1
vote
0answers
122 views

Does anyone have a copy of the paper describing the HiSeC™ algorithm?

I'm trying to create a remote controller compatible with HiSec algorithm. It's so old that “National Semiconductor” (now “Texas Instruments”) discontinued NM95HS01/02 and docs are unavailable. Does ...
2
votes
3answers
172 views

How are non-text files encrypted?

I thought encryption algorithms (like AES) are used to encrypt texts. So, how are files or folders (containing pictures, videos, etc.) encrypted? What is it that encryption algorithms exactly encrypt?
3
votes
1answer
116 views

Performing HMAC with random key before MAC comparison

In Laravel (a PHP framework) I can see that they calculate a HMAC with a random key over the final HMAC before comparison. This additional HMAC calculation is of course performed for both the ...
10
votes
1answer
140 views

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

Does anyone know the algorithm used by Turing's Colossus inference engine, so highly classified that the Brits kept it secret for decades after WW II? Indeed, it may still be classified. Several ...
7
votes
3answers
143 views

Would adding daily changing nulls in front of their messages have made the Engima harder to crack?

The British decrypted the German enigma because they knew that they would repeat the message key twice at the start of every message. Of course, technology to encrypt enigma without the repetition ...
1
vote
0answers
22 views

Proof that two signatures are done with the same short bases

My question is regarding lattice based signatures. Each lattice can have multiple short (secret) bases. Is it possible to proof in zero knowledge that two signatures on a fixed lattice have been ...
2
votes
1answer
119 views

Authentication protocol which detects client impersonation from another machine

Consider following authentication protocol. Client ClientA knows some initial secret KeyA shared with server. Client also knows IP of legitimate server. Now when client wants to establish connection ...
0
votes
3answers
361 views

CTR HMAC SHA256 implementation

After trying to invent my own AES mode, I decided to just implement something that's known to work, namely CTR with HMAC SHA256. From what I understand, I can use the IV as a counter, and the IV ...
-1
votes
1answer
40 views

How to tell if an audio stream is encrypted or corrupted? [on hold]

Is the following stream encrypted or corrupted? I was on a call and then this happened: http://vocaroo.com/i/s0PlF2s8ULAU
-1
votes
0answers
34 views

How we compute distance after lshashing? [on hold]

If we use an lsh function under l2 distance (hw,b(x)= ⌊ (wTx)/r ⌋ where w is a d-dimensional vector with entries chosen independently from a 2-stable distribution, r is a positive real number) or ...
0
votes
1answer
34 views

A5/2: Ciphertext Only Attack

A5/2 could be attacked with cipher-text only, using the Error Correction Code, in order to retrieve the session key. For the purpose of simplicity suppose that the error correction code copy the ...
1
vote
0answers
17 views

What is the exact algorithm and functions of the 4 way handshake?

I have to make a detailed diagram of the 4 way handshake and formulas for its functions so I need to know the exact process behind it. Like precisely what functions are used in it? I have been trying ...
4
votes
1answer
178 views

How should I read these three-dimensional (pseudo)random-generated numbers representations?

Visiting this site: http://lcamtuf.coredump.cx/oldtcp/tcpseq.html#phase I found graphical representations of random-generated sequence numbers, but I can't figure out how to interprete the plots. ...
0
votes
1answer
21 views

In Paillier homomorphism, how do you deal with bit length? [on hold]

I'm trying to figure out homomorphic encryption and would like to multiply two paillier encrypted numbers. Like so: [a].[b]=[a+b] To try this I got this Paillier.java and tried the following: <...
5
votes
1answer
123 views

How can I instantiate a generalized hash function?

I've come across a bunch of "strange" hash function notations, such as the following ones and now I don't know how to choose / instantiate them. Can you please explain me what this notation means and ...
8
votes
1answer
120 views

Could this “symmetric RSA” scheme provide key compromise resistant communications?

This question, and fkraiem's answer to it, made me wonder about the security and practicality of using "symmetric RSA" to provide a partially compromise-resistant secure channel. Specifically, assume ...
15
votes
2answers
248 views

Formal verification in cryptography

I have seen in some places that people use formal verification and/or computer-aided verification for cryptography (tools like ProVerif, CryptoVerif, etc.). How do these approaches work?
4
votes
1answer
56 views

Not-So-Simple Substitution Cipher?

The first go-to weakness when talking about substitution ciphers is frequency analysis. It assumes that there's a simple 1 to 1 character mapping between the plain text and the cipher text. Could a ...
2
votes
1answer
104 views

Forgery attack against Textbook RSA with simple redundancy

I know how to forge vanilla Textbook RSA message signatures (easy). I've learnt that by adding a good redundancy to the message, it cannot be forged anymore. How can one add redundancy so that the ...
1
vote
1answer
32 views

In Paillier homomorphism how do you substract?

I'm trying to learn homomorphism so the problem may also be in my code (which I will include). I want to compute $a - b$ where $a$ is bigger then $b$. In order to do this I tried to compute $\frac{a}...
6
votes
2answers
357 views

We can obtain “absolutely perfect CONFIDENTIALITY” using the one-time pad. Is there such a thing as “absolutely perfect INTEGRITY”? [duplicate]

The OTP (one-time pad) gives us perfect secrecy. This is the very best confidentiality available in this universe. (Although it does require large keys, which is beside the point of this question). ...
-2
votes
0answers
45 views

any post-shannon symmetric ciphers?

As far as I understand block ciphers use only simple operations to ensure good enough confusion and diffusion levels. meaning there is no math in it. "breaking a good cipher should require as much ...
2
votes
2answers
84 views

Calculating Polynomial Inverse with extended euclid in java

I'm trying to understand the NTRU-PKCS and therefor I wanted to code a naive Version of it. Now my Problem: I tried to calculate the inverse of a Polynomial with an extended Version of euclids ...
0
votes
1answer
31 views

Why is symmetric lightweight crypto only about block ciphers and not about stream ciphers?

Why is symmetric lightweight cryptography only about block ciphers and not about stream ciphers? AFAIK stream cipher implementations cost at least three times less than block cipher ones?
3
votes
0answers
39 views

Does changing the order of the steps within a round affect the security of AES?

I was trying to understand the internal structure of AES (Advanced Encryption Standard) Standard order of steps within a round: Substitute Bytes Shift Rows Mix Columns Add Round Key Substitute ...

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