1
vote
1answer
36 views

Given C is a code of length n. Containing M code-words with a distance d

I'm studying for my exam and came across this question below. I don't understand how to get $d$. I get $C$ is a code of length $n$. Containing $M$ code-words with a distance $d$. $(n,M,d)$ But how ...
3
votes
1answer
679 views

CBC-MAC length extension attack with IV simulation

I'm doing the Cryptopals challenges (formerly the Matasano challenges) and struggling with second part of the 49th problem where I'm asked to do the length extension attack with CBC-MAC without IV ...
2
votes
1answer
123 views

How does DH work when combined with ECC or RSA?

I know that Diffie-Hellman is used to create keys in a secure way over an insecure channel. But there is one thing which I cannot understand: I see that a lot of sites use ECC or RSA alongside DH. ...
2
votes
0answers
59 views

Are analog quantum computers a threat to RSA and DLP?

We already know that D-WAVE's "quantum computers" can't really run the Shor's algorithm, because the way they're built doesn't qualify them as universal quantum computers. Now researchers actually ...
9
votes
1answer
73 views

What's the reasoning behind the design of the TLS 1.2 PRF?

TLS 1.2 defines a PRF-like construction $P_{hash} : \{0,1\}^* \times \{0,1\}^* \rightarrow \{0,1\}^l$ for key derivation, etc. To quote the spec: We define a data expansion function, ...
3
votes
1answer
65 views

proof of correctness Ring-LWE cryptosystem

I've been studying Ring-LWE based crytposystems such as the one in this paper, but I can't seem to find/come up with a proof of correctness for this particular scheme. The encryption goes as follows: ...
0
votes
0answers
27 views

Password manager that uses a mix of long and short key derivation functions

I was reading "A Convenient Method for Securely Managing Passwords, Halderman et al., 2005". In short, the authors say to do the following: ...
4
votes
0answers
39 views

Quantum complexity of LWE

As per my understanding LWE is quantum secure because there is no known quantum algorithm to solve LWE in polynomial time. Due to the reductions given by Regev et al. If there is any algorithm that ...
5
votes
1answer
66 views

What is the most efficient attack on NTRU?

So, I got how finding the private key is equivalent to resolving the SVP. I also understood that the LLL algorithm can only be used in small dimensions. Now, I wonder what is the most efficient attack ...
3
votes
1answer
90 views

Salting Hash stored on RFID tag?

In my application, I am trying to prevent counterfeit widgets from being used on our gadgets; think HP ink-cartridges. I will be doing such with UHF RFID tags embedded in the widgets. Unfortunately, ...
1
vote
3answers
3k views

How to check the strength of an encryption algorithm?

I asking for advice on how to check strength of an encryption algorithm.
0
votes
0answers
55 views

Security Proof in Fuzzy Identity Based Encryption?

Been having a great deal of difficulty understanding the use of simulators to prove security of ABE schemes so I though I would start from the first ABE paper (Fuzzy Identity Based Encryption) to try ...
1
vote
0answers
12 views

how to create and use sub keys with PGP? [migrated]

let's say i wish to have forward secrecy with PGP, that requires me to create multiple sub keys to be used and destroyed accordingly, how should i do it?
4
votes
3answers
229 views

After a diffie hellman key exchange, what is the common secret used for?

What is the common secret that is established used for? What types of interactions are now possible?
4
votes
1answer
72 views

Enhance security by combining bits of 4 different hashes

Assuming that performances do not matter, is there any real benefit in terms of security (in general) in combine hashes in this way: hash functions: ...
3
votes
1answer
33 views

Conditions for Perfect Secrecy with the Vigenere Cipher

Please forgive my ignorance here as I'm far from a math major and I've never looked into cryptography before so if this seems stupid - it probably is. There is a question in a quiz I'm attempting that ...
7
votes
3answers
554 views

Did non-military cryptography appear in 50's and 60's only due to NSA leaks?

I'm not talking about scytale, but encryption like RSA, DES, etc... How did exactly civil cryptography evolve after World War II?
0
votes
1answer
59 views

Questions about length key of RSA 2048 bit

I use putty gen to generate RSA key, I choose length of key is 2048 bit, it generate public key: ...
-1
votes
0answers
23 views

Counter-Mode Message Authentication Code [duplicate]

Excuse my naivety,I don't know much about crypto. But I've been wondering, couldn't counter-mode be used for MAC just like CBC in CBC-MAC, assuming nonce for the counter is not repeated? Am I missing ...
5
votes
1answer
68 views

Are there any high level memory-hard PBKDF constructions?

The PBKDF2 construction from PKCS #5 v2 has the convenient feature that it can be implemented using only standard interchangeable cryptographic primitives. Specifically, it only requires the ...
16
votes
2answers
271 views

Is it possible for Alice and Bob to both sign a message “simultaneously”?

Let's say that there is a message which is considered valid if signed by both Alice and Bob. Alice could sign the message and then give it to Bob, so that he can sign it and give it back to her. But,...
1
vote
1answer
27 views

Can I use the Sequence Number as the (implicit) IV in AES-GCM IPsec?

The RFC https://tools.ietf.org/html/rfc4106#page-5 states that, under AES-GCM IPsec, each packet is expanded by 8 bytes for the IV and up to 16 bytes for the ICV. Why? Since we already have a ...
0
votes
0answers
22 views

Diffie-Hellman combined with DSA/RSA

we have learned Diffie-Hellman, RSA and DSA (Digital Signature Algorithm) in university. Because DH is vulnerable of Man-in-the-Middle we had the task to program the DH combined with RSA to protect ...
3
votes
1answer
107 views

Change initial hash value of SHA512/t

Fips 180-4 defines under 5.3.6 how to calculate initial hash values for SHA512/t for a given value t. Can someone explain me how the t actually affects the outcome of the procedure (which, as far as I ...
5
votes
1answer
664 views

What does this notation stand for when describing a code?

This code has appeared in some online course material. I understand the $(5, 4, 3)$ refers to (length, num codewords, distance) but no explanation of the $Z_2^5$ notation is given: One $(5,4,3)$ ...
45
votes
5answers
32k views

Can you help me understand what a cryptographic “salt” is?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can anyone offer me a ...
0
votes
1answer
33 views

factorization of an integer $N$ that is in special format

Suppose $p_0$ and $q_0$ are known prime numbers and define $p_i$ and $q_i$ as follows: $$p_{i+1} = next\_prime(p_i^2 + q_i^2), \qquad i \ge 0$$ and $$q_{i+1} = next\_prime(2p_iq_i), \qquad i \ge 0$$ ...
1
vote
0answers
31 views

Are public key and private key exchangeable? [duplicate]

If I get a key pair from RSA algorithm, can I make Private-Key public, and keep Public-Key secret without breaking the security of encryption and signature?
5
votes
1answer
80 views

Nonce for AES GCM to prevent replay attacks

I am wanting to encrypt a message with a pre shared key that uses AES GCM from the OpenSSL library to do so. I generate my key for the AES crypto via hashing my pre shared key with a salt using the <...
0
votes
0answers
26 views

What is the best approaches to find the type of a Cipher / Encryption? [duplicate]

There are many known and unknown encoding and encryption types / algorithms. When the algorithm is known, then at least it gives some direction or approach on what to do next to obtain the plaintext ...
0
votes
1answer
66 views

Key Hierarchy and key Encryption

If i have two 56-bit DES keys, and I use these two key to encrypt a 256-bit AES key. Like this $K_{AT}$ encrypts $K_{BT}$ and $K_{BT}$ encrypts $K$ What is the effective security of key $K$? Is it $...
16
votes
2answers
7k views

How does order-preserving encryption work?

Order-preserving encryption (OPE) is, apparently, a method of encrypting data so that it's possible to make efficient inequality comparisons on the encrypted items without decrypting them. I've been ...
3
votes
0answers
143 views

Inverting a candidate one way function

Let $w = a_0 \cdot a_1 \cdots a_{n-1} $ be a word from $ \{0,1\}^n $, $|w| = n$ Let $m = \sum_{i=0}^{n-1}{ a_i \cdot 2 ^ {n-1-i} } $ be the corresponding binary number constructed from the word. Let ...
48
votes
6answers
36k views

How can I generate large prime numbers for RSA?

What is the currently industry-standard algorithm used to generate large prime numbers to be used in RSA encryption? I'm aware that I can find any number of articles on the Internet that explain how ...
0
votes
1answer
27 views

Secure Cipher Suites supported by JDK versions [closed]

I'm a n00b to cryptography. I've been searching through oracle's java docs, ssl labs, googling and more googling attempting to find an up to date list of cipher suites considered secure for the ...
5
votes
5answers
237 views

Is it better to encrypt before compression or vice versa?

Is it better to encrypt a plain text file before compression, or vice versa?
4
votes
0answers
74 views

Security of Fernet Construction (wrt non self delimiting tokens and HMAC short key size)

Fernet is a described as a "high level symmetric encryption recipe" (source) that seems to be the default high level encryption scheme in the cryptography python ...
-2
votes
0answers
15 views

How does the input of (0..11) (512 bit) impact on the SHA-1 algorithm [duplicate]

If my H0(A0=B0=...=000hex) I think i wouldnt´t change anything and and my output for Round 1 would be K1 = 5A827999(hex)
0
votes
0answers
26 views

Error Detection/Correction Code-Then-Encrypt

I've just studied about the error correction schemes and encryption. First rule when using EDC/ECC is to first encrypt and then calculate them, and the major motivation we were told is that "EDC/ECC ...
4
votes
1answer
61 views

What is the recommended number of iterations for Argon2?

I've recompiled my operating system ("LionBSD" based on FreeBSD) to use Argon2i as the default password hashing algorithm in crypt/libcrypt. I'm wondering what the recommended number of iterations ...
5
votes
1answer
65 views

Difference between hierarchical and multi level secret sharing

In this paper, the definitions are simply as follows. Multi-Level secret sharing: Higher level participants can help lower participants to get the secret. Compartmented secret sharing: Each level ...
3
votes
1answer
115 views

Why should $a,b < N$ for Montgomery Reduction?

In Montgomery reduction, when calculating $a \times b \mod N$, it is required that $a \lt N$ and $b \lt N$. I think $0 \le T \lt N \times R$ is enough for the Montgomery Reduction. Rationale: Let $a'...
2
votes
1answer
119 views

Using e-ID Number for Encryption and Digital Signing

I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this. Generating PGP key-pair ...
3
votes
0answers
40 views

A few questions about CRC basics [migrated]

I am an electronic engineer and have not found it important to consider CRC from a purely mathematical perspective. However, I have the following questions: Why do we add n zeros to the message when ...
10
votes
1answer
438 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
11
votes
10answers
3k views

Are there any advantages in using proprietary encryption?

Proprietary software generally relies on the fact that in keeping the encryption algorithm private, it gets an extra layer of security implying "Security through Obscurity." Obviously this phrase has ...
0
votes
0answers
15 views

How much bandwidth is used in a typical IKE/ISAKMP initialization?

How much bandwidth is used in a typical IKE/ISAKMP initialization? How many UDP packets are sent in each direction, and what is their typical size? I'm referring to initialization of IPsec via IKE/...
2
votes
1answer
120 views

Quantum vs. regular computing time to break ECC?

How long exactly would it take for a regular computer to crack an elliptic curve public/private key via bruteforce, vs. a quantum computer using Shor's algorithm with a couple thousand qubits? Can ...
5
votes
1answer
258 views

How long does it take to decrypt an RSA/ECB encrypted message?

I am working on assignment where I have specific scenarios and I am little bit struggling with this one. Alice sends and email to Bob.For this e-mail, she uses the following method of encryption: ...
1
vote
2answers
95 views

Appropriate scrypt parameters when generating an scrypt hash

What values for CPU, memory and parallel difficulty should be used when generating an scrypt hash? i.e. ...

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