1
vote
2answers
54 views

What does $\langle A, B\rangle$ mean?

I'm reading about CL-PKC and in Al-Riyami's FullIndent, I find some notations I must be sure to understand, to well explain it ...
14
votes
2answers
229 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
2answers
46 views

Motivation for the definition of statistical distance

Statistical distance is a widely used measure in cryptography for comparing two distributions. One can define various other measures for capturing the differences between two distributions, but why do ...
2
votes
3answers
1k views

Comparing Files: Is it better to use multiple hash algorithms or just one?

I'm looking to compare (for byte-for-byte equality) two binary files. I already have the process down: Check for existence etc. Compare file lengths Use a hash or CRC of a sort (right now I use ...
2
votes
1answer
28 views

What is the diffrence between Feistel networks and SPN?

I recently read about the concept of Feistel Networks and Substitution Permutation Networks but what is exactly the difference between the two ?
3
votes
1answer
39 views

Order of multiple encryption algorithms

as you can see on image above, in VeraCrypt you can select either Serpent -> Twofish -> AES or ...
0
votes
0answers
38 views

Is this Commitment Scheme binding?

Commitment scheme is given as follows: Alice chooses a random r the same size as x and calculates $y = h(x||r)$ where $||$ represents concatenation. Open: Alice sends x to Bob, and Bob calculates $y ...
2
votes
1answer
898 views

Hash algorithm with the least chance for collision

Out of these algorithms… MD5 SHA1 SHA224 SHA256 SHA384 SHA512 … which has the least chance of collision, and which is the most secure at the time of writing this?
0
votes
0answers
9 views

Time complexity looking up in a rainbow table

It is mentioned in the famous paper Making a Faster Cryptanalytic Time-Memory Trade-Off by Philippe Oechslin that: The total number of calculations we have to make is thus $\frac{t(t−1)}{2}$. ...
-4
votes
0answers
32 views

You can probably do this in your sleep [closed]

I have been working on a geocaching puzzle for a long time I have solved all the ciphers except this: YLVEYF GIIKAH I have done what plain text attack I understand (mainly affine, one time and ...
4
votes
1answer
33 views

Which values to store in rainbow table generation?

According to the Wikipedia and Philippe Oechslin's Making a Faster Cryptanalytic Time-Memory Trade-Off (pdf), both starting points and endpoints are keys. Here is an example from Wikipedia: As you ...
5
votes
2answers
255 views

How many possible Enigma machine settings?

I'm trying to calculate the amount of settings the enigma machine has. I have found several sites regarding this topic, but it seems like there are two answers to my question. The first answer is ...
4
votes
1answer
61 views

What is the major difference between FIPS 186-2 and FIPS 186-4?

Can anyone please tell me the major difference between FIPS 186-2 and FIPS 186-4? I know with FIPS 140-2 they want the DSS standard to be FIPS 186-4, but what difference does it make?
5
votes
1answer
62 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
110 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 ...
2
votes
1answer
115 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 ...
-1
votes
0answers
33 views

A symmetric key construction not based on XOR [closed]

As far as I'm aware, one of the symmetric key constructions which is CPA-secure is $c = \langle r, m \oplus F_k(r) \rangle$. For designing a specific system I need a symmetric key construction which ...
1
vote
1answer
23 views

Single-scalar multiplication with sign bit

I want to know if there's an "easy" timing-free way to compute the sign of $y$-coordinate of $r G$, for a secret scalar $r$ and $G$ the generator of an elliptic curve. We have several choices for ...
2
votes
1answer
51 views

Get $a$ such that quadratic residue has a solution (Rabin)

My task is to implement Rabin signature. I have trouble with choosing padding a such that $$x^2 \equiv a \pmod n$$ has a solution. In that context, $n=p\cdot q$ is composite, where $p$ and $q$ are ...
4
votes
2answers
296 views

Security of the shared secret key for a smart meter (Linky)

Reading the specs of a new electricity smart meter (called Linky in France), I was surprised about the chosen encryption method (128 bits symmetric key AES), based on a single secret key (called CCC ...
10
votes
1answer
425 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 ...
0
votes
0answers
27 views

Deciphering encrypted / encoded tokens

I came across this token on the web ADEAAAFUu6sBKnmU_y-KDL5sm5lAAEN9IPqq1wY and was wondering how can one go about understanding what encoding or cipher is used ...
18
votes
3answers
39k views

Difference between stream cipher and block cipher

A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. A block cipher ...
0
votes
2answers
49 views

Need help choosing algorithm and topic [closed]

I am not pretty sure if this is the right place, but I have searched a lot and still cannot decide what to do. So here is why I am typing here - I am studying last year computer science and therefore ...
1
vote
1answer
71 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 ...
1
vote
1answer
41 views

How secure is MD5 for one way authentication?

I have a server S1 with an Private String (PS) as an identifier shared with a server S2. Every 10 min S1 publish the hash value of PS+the current time which is used as public identifier (PI). Every ...
2
votes
1answer
233 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: ...
4
votes
1answer
110 views

differential cryptanalysis cipher for the final round

I have a problem to find the sub-key. The system is… For each round, we make the following stage: We add the round key $K_i$. Substitution : we have 8 blocks of 4 bits, and an S-box ...
0
votes
0answers
22 views

How to approach to solve cipher text with fixed length key (which is repeating)?

I took a project to solve for lecture. In my project for a given cipher text(length 2031), I have a key (Picture of example is given.) which I do not know the length of it. So I started to try to find ...
5
votes
1answer
66 views

How many blocks can securely be encrypted with XTS

I could not find in the NIST recommendations on XTS how many blocks can securely be encrypted with XTS-AES. Through the recommendations, I've found: The length of the data unit for any instance ...
0
votes
1answer
36 views

What is proper size of window Using RSA Window method?

I want to Use Window method for RSA modular Exponentiation. because of SCA. But I don`t know what is proper window size.
-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 ...
4
votes
1answer
42 views

Multiplying two additively shared values

Alice has $p_a,q_a$ and Bob has $p_b,q_b$, all elements of a ring $R$. They want to obtain shares of the value $pq$ where $p=p_a+p_b$, $q=q_a+q_b$. How do they do this ? Does revealing their shares of ...
3
votes
1answer
58 views

How can I convert a mathematical formula into a logical formula?

I'm using cryptominisat2.9.6 to solve equation set (including more than 160 equations). There are 160 variables in total, which are as follows: ...
3
votes
2answers
69 views

Does a key need to be signed if it is being used to decrypt a message that is already signed?

I am trying to better understand authentication. Lets say I have posted my 128-bit AES symmetric key on some forum, encrypted asymmetrically to my friend using 256-bit ECC (25519). The forum isn't ...
1
vote
0answers
33 views

Possible enigma settings? [duplicate]

I'm writing an assignment about the Enigma machine, and i'm trying to calculate the amount of settings the enigma machine has. I have found several sites regarding this topic, but it seems like there ...
-1
votes
1answer
40 views

Can Anyone Suggest The Simple App To Encrypt Messages? [closed]

In the present scenario there are ways to snoop into someone's private communication. So in order to secure the communication encryption is the only way. Suggestions will be appreciated. Thanks
0
votes
1answer
48 views

Robust combination of two Password Based KDFs [closed]

I am researching some different constructions for combining two Password Based Key Derivation Functions in a robust manner to prevent weaknesses in a single algorithm from reducing the security of the ...
0
votes
0answers
36 views

How to decipher English letters that had been encrypted [closed]

I tried several decipher methods (here and here) but still cannot find any. How do effectively decipher those below. Below messages are English that had been encrypted. i) DBEJIXCV IWTDGN XH WDL ...
10
votes
1answer
2k views

Why not use CTR with a randomized IV?

I'm currently reading the chapter of Cryptographic Engineering (Ferguson, Schneier, Kohno 2010) about block cipher modes of operation. They have recommended CBC with random IV instead of CTR due to ...
0
votes
0answers
23 views

Garbled table for 3 inputs

I have a truth table of a full adder with 3 inputs (A,B,Cin) and 2 outputs (S, Cout). How can I create a garbled truth table? I mean, in the general form it is ...
4
votes
2answers
56 views

Need for 3 rounds in Luby Rackoff theorem

I get that using Feistel network we can create a secure PRP from a secure PRF (in 3 rounds according to theorem). My question is why not just 2 rounds of Feistel network is sufficient. Is it that ...
2
votes
1answer
54 views

Cryptanalysis of XOR cipher with repeated key phrase

My assignment is to cryptanalyze cipher text that we know was encrypted with a stream cipher (bitwise XOR of plain text and key stream), and decrypt to plain text. We know the key stream is a repeated ...
0
votes
0answers
10 views

Encoded Output to ASCII for carving into objects. [closed]

I have a piece of text that I need to carve out into an object after some encryption. For this purpose it works better if I have alpha numeric output instead of with any special characters (like I get ...
5
votes
1answer
38 views

Can one make a secure AEAD from any secure cipher and any secure MAC?

Can one make a secure AEAD from any secure cipher and any secure MAC using encrypt-then-MAC: with independent keys and IVs (any cipher and MAC) if the cipher is a stream cipher (including a block ...
2
votes
2answers
175 views

Cryptanalysis of Marvin32 compared to SipHash

So I am curious about the security analysis of Marvin32, the randomized hash algorithm used in .NET (to prevent hash-table DoS). I found the source code here: ...
3
votes
1answer
245 views

AES 128 bits with 12 bytes IV vector composed of a 4 bytes counter : safe?

I have a 128 bits AES cypher (GCM, Galois/Counter Mode) using a 12-byte initialization vector (IV) composed of: 8 constant bytes: 6 bytes (device ID) 2 bytes (zero) 4 bytes (incrementing frame ...
4
votes
1answer
68 views

How do I validate the AES cipher?

I have used AES CTR mode of operation. Each time a file is uploaded an encrypted file is obtained and the corresponding cipher is got – this is a mini project I have done. I wanted to know so as to ...
0
votes
1answer
67 views

Should I add randomness at the end before AES?

Seen AES, changing a character drastically affects the ecrypted text. I want to make it harder to decrypt AES I send. So, it seems this can be done by adding some special code and some random bytes ...
2
votes
1answer
53 views

Fixed primes in discrete logarithm

The discrete logarithm problem is to find $z$ when the inputs are $g,h,p$ where $g^z\bmod p$. Supposing if you fix $p$ then does the problem become any easier to attacks and is there a $(\log p)^c$ ...

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