1
vote
1answer
78 views

Multilinear Pairing in Cryptography

I want to create 2 Bilinear Pairing $e_1$,$e_2$ such that $$e_1:G_0 \times G_0 \rightarrow G_1$$ $$e_2:G_1 \times G_1 \rightarrow G_T$$ and use this to encrypt a message $M$ in the form $$M e_2(e_1(...
1
vote
1answer
46 views

Tackling encryption problems with “Zipf's law”?

I am new to cryptography and was wondering if it would be possible to semi-reliably "decrypt" an encrypted message by using the statistical distribution of symbols (/letters/numbers) in the encrypted ...
1
vote
1answer
66 views

what is meaning of operator “ := ” in cryptography?

I've seen := used in several cryptography papers where the this symbol has been used instead of assignment operator ($ \leftarrow $ ) or equal sign (=), but never with an accompanying explanation. It'...
1
vote
3answers
142 views

Is Threefish the only cipher with 1024 bits of security?

Threefish has up to a massive 1024 bits of security. Is it the only cipher with such overkill security?
1
vote
2answers
114 views

Understanding Hash function notations

I am implementing a Certificateless Cryptography Algorithm by referencing the paper An Efficient Certificateless Encryption for Secure Data Sharing in Public Clouds. In this paper on page no. 4 during ...
1
vote
2answers
91 views

Block cipher block and key sizes

Is there any point in making block size less than key size in block cipher? For example, Russian GOST symmetric cipher uses 256-bit keys to encrypt 64-bit blocks. That means there are many keys which ...
1
vote
1answer
256 views

Do I need to use a MAC with asymmetric encryption?

The internet has drilled into me that when I delivery any symmetrically encrypted data, I should also deliver a MAC to authenticate it before any decryption occurs. Do I also need to do this if I use ...
1
vote
1answer
59 views

What is the advantage of Pseudosquare?

Pseudosquares ,which are not square but Jacobi symbol are still 1, are used in some cryptographic algorithm. What is the advantage of them over the exact squares? If we used squares instead of ...
1
vote
1answer
63 views

What are the possible security issues when exporting a plaintext database to a file like this?

Say I have plaintext database with key-value pairs of usernames and passwords. Then I iterate through the database, encrypt the passwords, and write the username and encrypted password pairs to file ...
1
vote
1answer
74 views

multiplicative inverse in galois field $2^8$

I am trying to compute the multiplicative inverse in galois field $2^8$.The question is to find the multiplicative inverse of the polynomial $x^5+x^4+x^3$ in galois field $2^8$ with the irreducible ...
1
vote
1answer
48 views

ChaCha20 core vs ideal unkeyed PRP

I know that the ChaCha20 core (without the initial constant) is not an ideal PRP and must not be used as such. I also know that $\text{ChaChaCore}(0) = 0$. Are there any other differences?
1
vote
1answer
46 views

Is it possible to brute force a single smaller variable in $\operatorname{HMAC-SHA512}(k, a\ ||\ b\ ||\ c\ ||\ d)$?

Given $c' = \operatorname{HMACSHA512}(k, a\ ||\ b\ ||\ c\ ||\ d)$ and the 32-bit integers $a$, $b$, $c$, and $d$ is it feasible to alter $b$ and produce a valid MAC under the unknown key? I ...
1
vote
2answers
53 views

Merkle signature scheme

I was browsing the Wikipedia article on Merkle signature schemes and noted that it says: The number of possible messages must be a power of two[…] Why is that? ...
1
vote
1answer
41 views

What information about the ciphertext can an attacker discern if a key is used too many times?

Suppose that I use Blowfish or XTEA (both secure block ciphers with 64-bit block size) in CTR mode. In these cases, I need to change the key after $2^{16}$ blocks to avoid leaking information with ...
1
vote
3answers
126 views

Is all of encryption based on xor?

For a long time I've been under the impression that all of encryption uses xor at its basic level. Is this true? What other method could be used to encrypt plaintext with a key? Asymmetrically, as ...
1
vote
1answer
24 views

How is the usual way of using PKCS5/7 when a weird data is given?

PKCS5/7 pads the remaining data elements with a binary representation of how many space requires padding. This is useful and compact but what should I do in the following sample scenario below ? ...
1
vote
2answers
61 views

Unkeyed, fast, one-way PRP

Are there any fast, secure, one-way, unkeyed almost-pseudorandom permutations? I am looking for something that can hide a MAC, without requiring a secret key and while being much faster than public ...
1
vote
2answers
62 views

NIST HMAC Test vectors

I am searching test vectors of the HMAC-SHA256 primitive to verify the correctness of an implementation. Without hesitation I go on the NIST website to see what they offer. While reading the ...
1
vote
1answer
71 views

How to split up $GF(2^{128})$ into smaller fields?

I've heard that it's possible to split up $GF(2^{128})$ into copies of several smaller fields like $GF(4)$ so as to make the math easier in some cases. How do you do that? I know how it works for ...
1
vote
1answer
45 views

XOR or add in one time pads? [duplicate]

Is there any difference in adding the plain text and key vs using xor instead(apart from the performance improvements)?
1
vote
1answer
113 views

SHA256 for large files

I have a hardware engine for SHA256 which can process 64K of data, but the input data size I am getting is around 1MB. What should I do to process 1MB size. What should be my input after 1st 64KB ...
1
vote
2answers
41 views

Are there any disadvantages of using libsodiums helpers for en-/decoding/comparision instead of the native ones?

Libsodium has some helpers, which allow hexdecimal decoding, encoding and also constant-time string comparison. So if you use the php binding libsodium-php you ...
1
vote
1answer
414 views

How is El Gamal different from Diffie Hellman Key Exchange [duplicate]

I am Reading RSA and Public-Key Cryptography by Mollin and I can't make out how El Gamal is different from Diffie Hellman Key Exchange. Any thoughts?
1
vote
1answer
113 views

Is super encryption (aka “multiple encryption”) always good?

I'm trying to use super encryption (also known as “multiple encryption”) with AES in CFB mode with IV and password salting and AES in CTR mode both without padding. I first use AES CFB and then AES in ...
1
vote
1answer
56 views

What happens if you multiply a point with its order on complete Edwards curves?

I was recently working with some ECC crypto and stumbled across the following phrase on the SafeCurves page: The rational points of a complete Edwards curve are the pairs (x,y) of elements of ...
1
vote
1answer
83 views

What libraries do people use to implement and evaluate cryptography protocols?

I want to implement this credential system: “Anonymous Credentials Light” (PDF). The implementation would involve some zero-knowledge proof and some exponentiation. For some basic group computations ...
1
vote
2answers
291 views

Lightweight Asymmetric encryption algorithm

I'm an embedded systems researcher, and new in the crypto field. Actually, I need to know if there are any lightweight asymmetric encryption algorithm especially considering the time needed for key ...
1
vote
3answers
88 views

RSA message integrity

I wish to send some small data that RSA alone can encrypt, and I send a shared secret along with it. ...
1
vote
1answer
64 views

How are all necessary parameters shared between signer and verifier in ED25519 signature scheme?

I want to use ED25519 signature scheme in my application which requires frequent sharing of secret data between two entities in public domain. I know that Schnorr signature scheme has a key ...
1
vote
1answer
424 views

Decoding base64 encoded message with a key

I am pentesting a database that where I found data which was base64 encoded. I tried the usual method of decoding base64, which didn't work. Later, I found in ...
1
vote
1answer
80 views

Where can I get the correct and precise algorithms for elliptic curve cryptography?

I have been asked to implement cryptographic operations using elliptic curves. I would like to get precise algorithms for various processes like key generation, digital signature and verification. I ...
1
vote
2answers
131 views

Encrypt letters separately?

I am trying to encrypt the word Hello using RSA. When encrypting Hello’s integer representation, is each letter encrypted ...
1
vote
3answers
139 views

Adding dummy bytes to ciphertext

I was wondering if interleaving the resulting crypted data with dummy bytes placed at random positions but known in advance by the peers could improve security (no matter the algorithm and strength ...
1
vote
1answer
55 views

Hash functions vs. keyed hash functions in the context of private key generation

I'm designing a key distribution mechanism and have thought of using a securely generated/acquired private key as a seed for a sequence of private keys to be distributed to a number of users using a ...
1
vote
2answers
71 views

Paillier cryptosystem, small integers and range of values

First, this a different take on my previous question: Pailler encryption of small integers to 32-bit integers I have to encode small integers (range 0-50) using the Paillier cryptosystem. Those ...
1
vote
1answer
118 views

Birthday-attack calculation in planning password salting strategy

The book Cryptography Engineering by Fergusun, Schneier, Kohno section 2.7.1 explains Birthday Attacks: "In general, if an element can take on N different values, then you can expect the first ...
1
vote
2answers
232 views

FIPS 140-2 Compliance Testing

Is there any tool which can be used to test that implementations follow FIPS 140-2 Compliance ?
1
vote
1answer
168 views

Implement AES with 16 bit block size?

Can we implement AES with 16 bit block size ?if so what are its advantages and disadvantages?Is there any rule AES has to be implemented with 128,192,256 ?Can we use AES for odd number of bits(17,33,...
1
vote
1answer
88 views

Efficiency of McEliece cryptography (ciphertext expansion)

Most of the sources say McEliece has never gained acceptance because of its large size of private and public keys. However I have never heard about the size (or length) of its ciphertext. ("...
1
vote
1answer
99 views

have a question in the book “introduction to modern cryptography”

"introduction to modern cryptography. 2ed" in page 254 "By obtaining sufficiently many estimates and letting $x_{i}$ be the majority value, $A{'}$can ensure that $x_{i}$ is equal to $gl(x, e^{i})$ ...
1
vote
1answer
39 views

TLS Cipher Suite definitions

Based off the various cipher suites available for TLS (which I am looking at here:https://www.thesprawl.org/research/tls-and-ssl-cipher-suites/), can anyone clarify if when the suite contains 'SHA', ...
1
vote
1answer
55 views

Random Function size

I am new to cryptography. I have question regarding the size of the set of random functions. I found the text from "Introduction to modern cryptography" by Katz and Lindell, in another thread which ...
1
vote
1answer
231 views

Ensuring integrity and confidentiality together with symmetric encryption

I've been required to answer a question: As usually, we have Alice and Bob. Suppose Alice wants to send a file F to Bob, ensuring integrity and confidentiality. They share a symmetryc key $K_{...
1
vote
2answers
165 views

Is entropy being lost when the hash of a secret has a specific format?

Bitcoin's mini private key format works by brute forcing random data to produce a secret so that when appending ? and then hashing with sha256 it will produce a ...
1
vote
1answer
299 views

Simulation Based Proof: What Can / Can not Simulator Do?

I have seen some examples in "Foundation of cryptography" and "Efficient two party computation", in which simulator can do some things that in the real world model the parties cannot do, for instance: ...
1
vote
2answers
86 views

Collision probability of MD5 over different attacks

I am researching the collision probability of MD5 and various attacks against it. Can someone help me how to learn the least probability that there will be a collision in a specific attack on MD5? ...
1
vote
1answer
201 views

Is this hypothetical key-exchange secure?

I've thought about the following (generic) key-agreement protocol. The only weaknesses I could have found are missing freshness guaranteees. As for the notions: $E^1_K(P)$ is the symmetric encryption ...
1
vote
4answers
131 views

How is an epsilon of 1/1000 non-negligible?

Lately I've been studying cryptography and in the current course I'm taking we're reviewing statistical tests and how they can be used to determine if a pseudo-random generator is secure or not. ...
1
vote
1answer
154 views

Reversing Rotation + XOR

I have this cypher which is as follows : Take 2 numbers : A=1011 and B=1010 if the ith bit of A is 1 then shift B i times to the left. So in the end you will get ...
1
vote
1answer
108 views

Will adding space to the Vigenère block make it truly unbreakable?

I just have gotten into cryptography and learned about the Vigenère block. I think it's a very good idea because, if used correctly, it is unbreakable. But the only downsite is, the key must be the ...

15 30 50 per page