# All Questions

18,380 questions
2 views

### Digital Signature Algorithm for large files - bottle-necked by hash function?

I am new to studying digital signatures like ECDSA and EdDSA, and was curious about something. Lets say hypothetically I want to create a digital signatures of millions of files, with a total size of ...
13 views

### Big-O Encryption Algorithm

I am currently doing a research paper on the Blowfish encryption algorithm and one of the components that I need to include is time and space complexity. I have tried reading academic articles and ...
122 views

### Is GMW different from Secret Sharing?

Is GMW (How to play ANY mental game) protocol different from Secret Sharing?? If so, how is it different from Secret sharing?
21 views

### Is there a standard definition of non-malleability for the encryption schemes?

I find some different definitions of non-malleability for the encryption schemes. They may be equivalent, but I am not sure which one is better or if there is a standard definition. I give two ...
17 views

### PKCS#10 why keeping the Subject Public Key in the X.509 Certificate

In the pkcs#10 workflow to obtain the x.509 certificate used in digital signature, in the Certificate Request Information, itself in the CSR, we have the Subject Public Key. That Subject Public Key ...
164 views

### Generate PGP keys very very fast

Is there a way to generate thousands of PGP keys at a very very fast rate? I am generating thousands of 3072-bit PGP keys looking like part of a personal research project. Obviously, this is a very ...
89 views

### RSA key problem

So I have the cryptographic task. There is a problem with the encryption, and I need to find a way to generate private keys out of the public. There is what I have. The private key generated by ...
82 views

### Low entropy - how does it compromise the crypto

One of the often pointed out mistake in dealing with crypto is not having enough entropy in the system. Without enough entropy the random numbers generated are not random enough. But what I am not ...
152 views

### What are some real world examples where one time pad encryption is used or can be used?

I understood that One-Time Pad (OTP) encryption ensures perfect secrecy. However, I couldn't find any real-world examples where the OTP is used. Also, which are some real-world examples where it won'...
20 views

### Twist on Elliptic Curve defined over an extension field [on hold]

I am trying to compute the quadratic twist for an example of an Elliptic curve defined over a $GF(p^8)$ Field: With p=...
31 views

### BGN encryption scheme with unbounded message space

In Evaluating 2-DNF Formulas on Ciphertexts stated that decryption in this system takes polynomial time in the size of the message space T. Therefore, the system as described above can only be ...
30 views

### Division using Fully Homomorphic Encryption

When I am not allowed to do interaction with server, then I use Taylor approximation for division in non-interactive process. Let's say that I am allowed to do interactions with server. I have ...
57 views

### NIST randomness test p values

I have a binary sequence of length $2^{20}$. I am using the NIST statistical test, assess. What should be taken for ./assess and ...
31 views

### Subtracting one pederssen commitment from another

I am building a range proof to prove that a secret number x lies between a specific range a prover commits to a values a<x<b prover generates a pedersen ...
15 views

### what is the relationship between epsilon and sensitivity in the Differential-Privacy?

In some Differential-Privacy(DP) papers, they use epsilon as the x-axis in the figures of the experiments' result while other papers use the sensitivity. What is the relationship between epsilon and ...
29 views

### How secure is a book derived key and what can be done to strenghten it?

If you have a manual encryption system where the keying is done by extracting a key from a book, a major weakness is that an adversary can search trough all existing books to find a perfect Match and ...
44 views

### How to apply lagrange interpolation on bilinear pairings?

I have seen in some places applications of Shamir secret sharing and lagrange interpolation mixed with bilinear pairings, however I fail to understand how this works. For instance, here I find the ...
12 views

### Django Web API hosted in IIS - shared file acces [on hold]

I have create Django rest api and deployed in IIS.. I am trying to access a shared folder on another server.. And has give access to a domain user which is the Site anonymous user and app pool ...
55 views

### If OAEP is introducing randomness to encryption how could be ciphertext decrypted?

I was studying OAEP and see we introduce a random value $r$ when computing the padding. See the figure below from Wikipedia So if we are adding randomness to encryption, how could this ciphertext be ...
2k views

### 80-bit collision resistence 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 ...
33 views

### Purpose of the ZKPoPK in the original SPDZ protocol

What is the purpose of ZKPoPK in the SPDZ paper? And will the following can detect the active adversaries in 2 party spdz excluding ZKPoPK step? Each party sends a commitment on his MAC key ∆_i ...
28 views

### Is there any point to encrypting a file if it's transferred via ssh?

Suppose I have two machines which can ssh into each other. Is there very little point in using gpg with a password protected symmetric cipher to transfer a ...
36 views

### What is chain voting?

I read The ThreeBallot Voting System by Rivest. This paper-based voting system can be attacked with chain voting. But can't find any description of what "Chain voting" is mentioned in section 4.9. ...
33 views

### trapdoor commitment from lattice-based assumptions?

I'm wondering that is there any equivocal commitment scheme (i.e., trapdoor commitment) can be constructed from lattice-based assumptions? I know there are a lot of commitment schemes from lattices as ...
28 views

### What is the security model of the FHE system introduced in Fully Homomorphic Encryption Using Ideal Lattices?

How would one construct a security model to play against the adversary, and define the security of the overall scheme? This is in reference to the scheme introduced in "Fully Homomorphic Encryption ...
33 views

### Is computing majority element while doing secure two party computation for inner products ( input of the two parties ) an attack on the protocol?

This was told to be an attack. However, we can create a simulator in the ideal world which sends all 1s to the trusted party and receives the number of ones of the honest party. Is this simulation ...
62 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?
2k views

### Are encryption algorithms with fixed-point free permutations inherently flawed?

Flaw in Enigma One of the Enigma machine's flaw was the derangement (fixed-point free permutation) of the produced ciphertext, or simply put: No plaintext-letter can be enciphered to itself. See this ...
90 views

### Fermat's factorization method on weak RSA modulus

Given a public key for RSA, I have extracted the modulus which looks like this: ...
486 views

### Truncating the output of AES-128

I'd like to use the output of a pseudorandom function (PRF) as a one time pad. I want to use AES-128 (as it's commonly used as a PRF). As we know AES-128 output 128 bits. Question: Would be secure ...
33 views

### Time-based decryption service

i am thinking about building a public crypto service, yet at the same time, I am still quite new to crypto and therefore prone to snake-oil inventions I guess. My plan is to build a website which ...
69 views

### Elliptic curve ed25519 vs ed448 - Differences

Other than key size, What are some differences between the Elliptic curve ed25519 and ed448?
59 views

### What is the time complexity of computing a cryptographic hash function/random oracle?

I'm wondering what's the computational complexity of computing a hash function/random oracle when doing complexity analysis. For example, what's the computational complexity of computing $H(b\|r)$? ...
49 views

### Does SHA1 require public keys? [on hold]

I want to know if they do, and if they don't which ones don't require public keys.
55 views

### PRG in a stream cipher [on hold]

Alice wants to encrypt a message for Bob using a stream cipher built from two candidate PRGs, call them G1 and G2. The goal is that if either is a secure PRG, the resulting cipher is a secure stream ...
20 views

### Brute atack force affine cipher [on hold]

help me please, I really need the code Program (Pascal or C) for encryption and decryption, the cipher affine whith brute force attack
79 views

### What is the difference between a Vigenère cipher and a one time pad cipher?

I'm doing a decryption competition at a nearby college. We are allowed one cheat sheet so I'm trying to make one. I realized that the Vigenère cipher was very similar to the one time pad and wanted ...
68 views

### What are known metrics for TRNG?

I was wondering what the known metrics are for studying the randomness of TRNG (besides NIST tests). For example, for PUFs, there are known metrics such as uniformity, uniqueness, BER, etc.
31 views

### Which 'info' and 'salt' parameters to use in HKDF for TLS 1.3?

all the following discussion is for HKDF in TLS1.3: Regarding the 'salt' parameter in - HKDF-Extract(salt, IKM) as written in RFC 5869: HKDF without having to protect the secrecy of the salt. In ...
35 views

### UC-framework: Simulating specific cases (proof in PVW)

I am struggling to understand the proof of security in the UC-framework of the OT by PVW. The cases I don't understand are the cases where: i) Both parties are corrupted. In this case, they say ...
60 views

### In cryptocurrency they use Secp256k curve. Can someone generate private key with different curve?

A lot of cryptocurrencies is using Secp256k1 (for example: https://en.bitcoin.it/wiki/Secp256k1). Every cryptocurrency library comes with its own redundant implementation of Secp256k1, ECDSA, ...
63 views

### Definition of symmetric cipher and definition of asymmetric cipher

So I'm currently taking a cryptography class right now and my professor has told the class that she can't even define symmetric cipher for us without getting into asymmetric ciphers and the textbook ...
651 views

### Can you recognize a low private exponent from a public key?

In the RSA cryptosystem, Wiener, Boneh and Durfee showed that low private exponents can be efficiently recovered. Is it possible to see from a public key alone whether the private exponent (d) is ...
34 views

### what type of the cryptographi operation is done? [on hold]

I was reading a cryptography article recently and faced the section which I could not understand it is there anyone to describe it completely thanks
11 views

### Standard deviation of gaussian noise in FHEW scheme

I've got two questions regarding the paper FHEW: Bootstrapping Homomorphic Encryption in less than a second. First, the final error of a ciphertext after the refresh procedure is stated as following ...
61 views

### Hash for use in embedded HMAC application

I developed a GNSS logger (http://flysight.ca) which has become popular for scoring skydiving competitions. At the moment, there is little protection against competitors falsifying tracks, but I would ...
91 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 ...
29 views

### EC non-shared cryptosystems - different group for every party

Efficient Identity Based Parameter Selection for Elliptic Curve Cryptosystems by Arjen K. Lenstra contains a proposal for a non-shared elliptic curve cryptosystem. Every party chooses its own field ...