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5
votes
1answer
179 views

Full encryption of IDs, partial decryption with customer specific key

I am looking for a "partial" encryption/decryption algorithm. Let's say I am encrypting the following List of IDs (long values) $[1,2,3,4]$ (with a secret key) to an encrypted string $e$, I would ...
3
votes
0answers
41 views

Election communication protocol

I'm not a cryptography expert, but this seems like it falls into this area. Imagine I want to design an election system (senate race for example) where I send the exact same ballot of 100 candidates ...
1
vote
2answers
135 views

Verifying Without Knowing Key

Say user Bob sends an encrypted message to a server. People can download the message from this server and later get the key directly from Bob. Is it possible for the server to somehow verify that ...
9
votes
1answer
183 views

State recovery of Micalli-Schnorr random number generator modulo a prime

Let $p$ be a public prime of $n$ bits. Define the sequence $x_i=z_{i-1}^e \bmod p$, where $z_i$ is the $k$ high-order bits of $x_i$, and $r_i$ the remaining $n-k$ bits of $x_i$ (thus ...
5
votes
2answers
199 views

Finding the subgroup in isogeny-based cryptography

Isogeny-based cryptography is one of the newest post-quantum cryptography. Hardness of this system is based on finding isogeny between two elliptic curves. Also this is theorem: Elliptic curves ...
-1
votes
1answer
33 views

Documents about ZUC

ZUC is a function that converts a string to another string. However, unlike a Hash function, ZUC converts a certain-length string to a any-length string. Can someone point me to its documentation or ...
3
votes
1answer
112 views

ElGamal Signatures

I know various applications of RSA signatures. I wonder, is there any real-world applications of ElGamal signatures and encryption?
1
vote
1answer
185 views

Choosing primes in the Paillier cryptosystem

In the first step of key generation phase in Paillier cryptosystem given here. It's given that $$\operatorname{length}(p) = \operatorname{length}(q) ) \implies ...
1
vote
0answers
57 views

How to normalize data of a generic HTTP request for the purpose of signing

I am working on PowerAuth 2.0, a solution for counter-based signing of HTTP requests (for the purpose of mobile banking). One of the tasks that I solved somehow but I am still not happy with the ...
3
votes
1answer
60 views

Block cipher mode of operation with beyond-birthday-bound security

I am looking for block cipher modes of operation that are secure even when the number of blocks encrypted exceeds the birthday bound.
1
vote
0answers
32 views

Does a password that's cracked someone's account increase the chances of cracking someone else's account?

For every find in password that cracks someone's account, does that particular password have a higher probability of cracking someone else's account more than a brute force dictionary choice? How ...
24
votes
1answer
3k views

Examples of modern, widely used ciphers that suddenly fell?

RC4 and GOST are two major ciphers (defined as being widely used to encrypt large amounts of data) that fell to cryptanalysis (relatively) suddenly. The first becoming totally broken and the second ...
6
votes
1answer
90 views

Is every point on an elliptic curve of a prime order group a generator?

If the order of elliptic group is prime then every point is a generator of that group. I tested the above statement on some elliptic curves and found it true. Does that really work on all curves? Is ...
3
votes
1answer
38 views

How are the IVs of SHA512/256 and SHA512/224 calculated?

This seems odd to me, because there are a lot of resources out there saying that the initializer values of SHA512 and SHA384 are the first 64 bits of the fractional parts of the square roots of prime ...
1
vote
1answer
128 views

CP-ABE for threshold cryptography

I would like to know if there is any research work using CP-ABE for threshold cryptography? I want to know also if applying CP-ABE for threshold cryptography would overcome other techniques.
1
vote
0answers
61 views

What functional encryption scheme can be used to compute a linear function?

I am looking for a functional encryption scheme that can compute a linear function. I do not need to work with attributes. All I want is to compute the result of a function $y = a*x+b$, where $x$ is ...
9
votes
5answers
341 views

Which cryptography technique does not increase the size of the plain data?

I want to encrypt some data(text/voice/video) but it is essential that the size of the cipher data remains the same as the plain data. Which techniques can I use, and how secure are these techniques ...
0
votes
2answers
211 views

DES hardware implementation of substitution lookup table [ ReWorked ]

I'm a crypto enthusiastic and student of cryptography. I'm developing a project with other students titled "A hardware implementation of a DES cryptography for educational purposes", our idea was to ...
14
votes
3answers
2k views

Webcam random number generator

I have a question about random number generators. I have read from a real random number generator, based on a webcam ("randcam"). My problem is, that I do not really understand how the generation of ...
1
vote
0answers
131 views

Example describing Baek and Zheng’s threshold identity-based decryption scheme

I am trying to work through an example of Baek and Zheng’s “threshold identity-based decryption scheme” and I tried a lot to solve this, but somewhere I’m doing something wrong. I hope someone can ...
7
votes
3answers
290 views

What was the first MD5 collision ever constructed?

We all know that MD5's collision resistance is severly broken. But when thinking of "random" strings with great cryptographic importance I've come up with NIST's curve seeds and MD5 collisions. But ...
1
vote
0answers
54 views

Does using a verifiable secret sharing scheme ensure robustness of a protocol if it is secure under the semi-honest adversarial model

Consider a protocol $\pi$ which uses a linear secret sharing scheme like that of Shamir secret sharing. Further assume that the protocol $\pi$ has been proven to be secure (correctness and privacy) ...
1
vote
1answer
39 views

Attacks on schemes based on elliptic curves when the transmitted points are not on the curve

Some elliptic curve schemes require to send a curve point during the normal execution of the protocol. For example, ElGamal encryption and ElGamal signature require this. On the other hand, ECDSA does ...
5
votes
4answers
1k views

Security proofs for CBC mode

I'm looking for different approaches to proofs for the security of CBC mode encryption. What are the best sources of information about this subject?
4
votes
2answers
99 views

Are there simpler FHE methods than Craig Gentry's original paper?

Craig Gentry's 2010 paper on FHE is very cool, and I'm planning on implementing a basic proof of concept FHE. I was wondering though, are there any simpler methods that have been discovered since ...
9
votes
0answers
105 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 ...
4
votes
2answers
587 views

Update to “Cryptographic Right Answers”

I'm a big fan of Colin Percival's "Cryptographic Right Answers" post. This was written in 2009, which is a long time ago in Internet years. Is the advice still valid or, if not, can someone point me ...
21
votes
1answer
788 views

Proof for the SHA3 claim that 256 bit security is “post-quantum sufficient”?

On page 14 of "Keccak and the SHA-3 Standardization" (February 6, 2013) it says: Instantiation of a sponge function the permutation KECCAK-f 7 permutations: b → ...
4
votes
1answer
54 views

VIC cipher author known?

Does anybody know if the design of VIC cipher is attributed to anybody? I've tried Google and found nothing. There are quite a few sites describing the method in detail, a few implementing it ...
3
votes
1answer
48 views

What are fixed points and length extension attack in hash functions?

I was recently reading about hash functions, and I came across fixed points (one or more fixed points, interested in both) and length extensions, but I didn't exactly understand how these work. If ...
4
votes
1answer
40 views

Generate a random number $r \in \{1,2, \dots , k\}$, where $k$ is not public and is distributedly held

A set of parties can securely generate a random number $r \in \{1,2,3,\dots, k\}$ when $k$ is publicly known. However, can we generate the random number $r$ if $k$ is not publicly known and is held by ...
4
votes
1answer
201 views

Discrete logarithm problem is easy in a cyclic group of order a power of two

Let $G=\langle g\rangle$ be a cyclic group of order $2^{k}$ and let $h\in G$. I have read that it is easy to find $\log _{g} h$, but I haven't been able to figure out how. Do you know why this can be ...
2
votes
0answers
29 views

RC6-like key schedule with 16-bit S-boxes

I am trying to figure out an encryption algorithm whose key schedule function seems to be similar to RC6. However, it seems to be creating S-Boxes using 16-bit integers instead of 32-bit ones. I have ...
3
votes
0answers
31 views

What is the current encryption method used on GSM currently?

I am currently doing a mini project which sniffs GSM packets using gr-gsm and wireshark. I was wondering if anyone knows what is the name of the current encryption algorithm method used on GSM?
3
votes
1answer
49 views

Identity-based proxy re-encryption using different system parameters

I am wondering if there is an identity based proxy re-encryption scheme (such as the Green-Ateniese scheme https://eprint.iacr.org/2006/473.pdf) that converts an encryption computed with ID1, system ...
5
votes
2answers
105 views

Where did Martin Hellman acknowledge Ralph Merkle's contribution to public-key cryptography?

I am trying to find the article to reference when discussing the Diffie-Hellman key exchange. According to Wikipedia Hellman said that The system...has since become known as Diffie–Hellman key ...
3
votes
4answers
656 views

A mathematical explanation of the DES encryption system

I need a mathematical explanation of what does the DES encryption system really do. This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
-1
votes
2answers
85 views

How do they implement MAC in TLS?

I recently read questions about "MAC then Encrypt/Encrypt then MAC" which made me curious about how they actually use the algorithm. MAC only calculated once either case (according to what I read). ...
4
votes
0answers
61 views

Are there any test vectors for the CMS content type AuthEnvelopedData (for AES-GCM)?

I am looking for CMS AuthEnvelopedData test vectors for AES-GCM mode. I haven’t seen any ready-to-use test vectors for it. There are test vectors for AES-GCM mode but not for its CMS support. I even ...
7
votes
1answer
253 views

Where is CFB-MAC defined?

I can find descriptions of using CFB mode to create a MAC and even implementations, but cannot find any standard or papers analyzing its security bounds. Is there a standard for CFB-MAC? Where can I ...
8
votes
2answers
423 views

How to do a literature search

How do I do a literature search of the research literature on cryptography? Assume there's some topic in cryptography I'd like to learn more about; how do I search the cryptographic research ...
4
votes
1answer
103 views

How to generate fingerprint for PGP public key

I would like to know how to generate a fingerprint for an openPGP public key. To be clear, I'm interested in how the fingerprint is generated. I'm aware that I can get the fingerprint with a ...
0
votes
1answer
58 views

How does a user register his verifier at host in SRP (Secure Remote Password) protocol?

I read RFC 2945 and 5054 describing SRP, but there was no mention of registration. How should user registration happen in SRP? Is there a standard or paper describing it?
10
votes
1answer
405 views

Status of Algebraic Eraser key exchange?

Algebraic Eraser™ is a relatively new asymmetric key agreement protocol (also designated the Colored Burau Key Agreement Protocol), based on a simultaneous conjugacy search problem in a braid ...
2
votes
1answer
114 views

State of the art techniques for Anonymous Authentication?

What are the state of the art techniques for Anonymous Authentication? What are the most popular ones? The problem domain I am considering is with respect to different users accessing cloud content; ...
8
votes
1answer
110 views

A general definition for cryptocurrencies

I am trying to find the definitions to several terms related to digital currencies. Unfortunately, I am always ending up on Bitcoin-oriented pages and websites which only take Bitcoin itself into ...
1
vote
2answers
208 views

Is there an algorithm to hide text in another text, while preserving the meaning of the latter?

Is there a way to hide a text message $A$ inside another text $B$ using a cryptographic cipher/algorithm, while preserving the sense/meaning of $B$ and without anybody being able to notice there is a ...
5
votes
1answer
109 views

Are there any long term RC4 bias based exploits?

The RC4 cipher possibly exhibits low level bias in it's long run PRNG keystream. I'm specifically excluding short term bias attacks which I'm defining as outputs < 1024 bytes. Are there any real ...
0
votes
1answer
209 views

Self-Convergent Hashing

What is the name of an algorithm that hashes its result as an embed of larger set of data that results back to the hash? For instance where $f(x)$ is the hashed result and $x$ is the dataset, and ...
3
votes
1answer
535 views

How to prove that a function is not pseudorandom?

I am currently enrolled in a cryptography course, which uses the book by Katz and Lindell. I'm struggling with the exercies which ask for proofs, like the following one: Let G(k) be a PRG with ...