0
votes
1answer
18 views

Winternitz Signature Scheme Verfication

I am reading page 39 in this "Post Quantum Cryptography" book. Why does equation 15 hold? There is no further knowledge about f and you definitely cannot use any power laws. So, why is ...
0
votes
0answers
6 views

Constructing set membership proof for private set

Is it possible to construct a set membership proof to show $\delta \in \Psi$ where $\delta$ is publicly known and $\Psi$ should stay only known to the prover? It seems rather impossible but I would ...
0
votes
0answers
33 views

My attempt of solving socialist millionaire. Is it good?

I've come up with an algorithm to solve the socialist millionaire problem, but I'm not sure if the algorithm is secure. I wasn't able to find any flaw in it, but it seems too simple to be secure, so ...
-1
votes
0answers
8 views

AES Encryption using CBC/PKCS5 padding in python while decrypting in java it is given below error

Can any one help me while encrypting using CBC/PKCS5 padding in python while decrypting in java it is given below error javax.crypto.BadPaddingException: Decryption error at ...
-2
votes
0answers
8 views

What is padding PKCS5? How to encrypt the text data using IV key AES/CBC/PKCS5 in Python

hi am new to python coding,can anyone please give me exact information rearding PCKS5 padding and then about the encryption using IV key AES/CBC/PKCS5 in Python
0
votes
1answer
30 views

Can you identify this algorithm? [on hold]

We are attempting to integrate our application in to a third party system. To do this we need to pass encrypted passwords in to this system. I have decompiled the assembly and looking at the code it ...
1
vote
1answer
15 views

Differences between HMAC and HKDF in a specific case

I want to use a key derivation function to derive a key to another one. I think HKDF is the easiest solution in my case. The following picture gives a clear definition of it : ...
0
votes
1answer
34 views

security in format preserving encryption

In format preserving encryption an attacker knows the format and data type of the plain text. The format of the plain text and cipher text are same. usually cipher text are unreadable form. then how ...
0
votes
2answers
60 views

Can AES be considered as Perfectly Secure?

I am studying about the AES encryption standard, and as I know from the theory there is no known weaknesses today about this block-cipher. I would like to find out or at least to understand what ...
1
vote
1answer
22 views

What is the right notion of security to use for file encryption?

It seems that several file encryption systems do NOT use authenticated encryption. (E.g. gpg --symmetric and boxcryptor as far as I can determine). I understand that this is generally considered ...
0
votes
0answers
23 views

Is there a mental poker algorithm that does not rely on commutative encryption?

The algorithm for mental poker that I saw on Wikipedia and everywhere else relies on an encryption algorithm such that $E_k(E_j(P)) = E_j(E_k(P))$, but I can't find a modern and secure algorithm for ...
1
vote
1answer
52 views

About Primitive roots mod n in Diffie-Hellman

I'm on the study of Diffie-Hellman and its related math (multiplicative group of integers mod n). In some crypto papers and documents I've read that 'g' needs to be a primitive root mod n ('g' order ...
1
vote
0answers
26 views

Why does OMAC2 exist?

The specification for OMAC has the following to say about OMAC2: For OMAC2, we adopted u−1 instead of u2 as Cst2. It requires one right shift to compute L· u−1 instead of one left shift to compute ...
2
votes
0answers
31 views

DPA Attack on HMAC SHA-256

I have read the paper "Differential Power Analysis of HMAC SHA-2 in the Hamming Weight Model" (http://www.di.ens.fr/~belaid/articleHMAC.pdf) and I want to understand the DPA Attack. In section 3.2.1 ...
0
votes
3answers
77 views

Fast PKI for embedded device

We are creating a device with a small microcontroller (20 MHz CPU 16 KiB RAM). We need some way to securely send signed files to device (only signature, no encryption necessary). An external company ...
0
votes
0answers
15 views

Encoding info for different SaaS users [on hold]

My company is developing a management software and we want it to be SaaS. Now we face a crucial question: how do we ensure our clients that we cannot access their data from the server? Which is the ...
-1
votes
0answers
27 views

What are these: b04bmtpf b00k8fdx b052hdnr b04d4p0b [on hold]

I'm trying to understand how the BBC sets its URLS. Each program on the BBC has a url like http://www.bbc.co.uk/programmes/b04bmtpf or http://www.bbc.co.uk/programmes/b04d4p0b Where the last 8 ...
0
votes
0answers
26 views

Is end to end email encryption possible without unique domain/subdomain for each user? [on hold]

Lets say Alice@gmail.com wants to send message to Bob@secureMail.com Alice <--> gmail.com <--> secureMail.com <--> Bob We know gmail.com can read the unencrypted message. Is it possible for ...
0
votes
0answers
25 views

Reducing the degree of polynomial descripting a block cipher [on hold]

Any one knows about Reducing the degree of polynomial descripting a block cipher? Regards.
0
votes
2answers
45 views

How to decrypt a PGP message with only the two primes and the public exponent?

I'm trying to decrypt a PGP Message that is encrypted with an RSA key, but I only have this information: Public exponent: 65537 Prime 1: ...
0
votes
2answers
52 views

Operation modes of block ciphers how are used?

I am studying about different operation modes of block ciphers my question isn't something specific to that, but is how these operation modes are used in cryptography? I have this picture here ...
0
votes
0answers
24 views

poodle padding multiple blocks?

I'm quite new to the topic and read a bit about poodle and padding oracle. I quite understand the "regular" padding oracle attack, substituting the last byte of block(n-1) to determine the last byte ...
-1
votes
0answers
45 views

One-time-pad with multiplication [on hold]

Does a one-time-pad with multiplication instead of xor between the message and the key introduces security problems?
1
vote
0answers
38 views

Non-interactive zero-knowledge proof for discrete logarithm without random oracle

Is there any non-interactive zero-knowledge proof for discrete logarithm without random oracle over the group $\mathbb Z_p$?
0
votes
4answers
110 views

Why don’t all AES encryption tools produce the same key from the same password?

Alice and Bob meet regularly. They have agreed face-to-face a 128 bit password which they want use to encrypt/decrypt emails written between them. They decide to use 256-bit AES. Alice wrote her ...
0
votes
1answer
41 views

Does the encryption algorithm DES perform random permutations? If so how is information not lost?

"Before round 1 begins, all 64 bits of an incoming message and all 56 bits of the secret key are seperately permuted (shuffled)" My question is this : Is the shuffling of the bits performed randomly? ...
1
vote
0answers
42 views

Why is public key cryptography not widely used in governments? [on hold]

Are there any practical limitations? Govt driving license, passport, SSN could be digitally signed making it easy for anyone to validate. They can have a qr code in them which can be easily validated ...
4
votes
2answers
232 views

What does a stream cipher provide that cannot be obtained with AES CTR mode operation?

I can precompute the key stream for the CTR mode operation and the encryption at that point is similar to a stream cipher. So why are there stream ciphers still used and proposed after RC4? Recently ...
0
votes
3answers
52 views

One time pad in CBC mode?

I have been searching about if it is more secure to use CBC mode in OTP but I can't find anywhere where people have sad that it is more secure. Question: Is CBC mode in OTP more secure? Because I ...
0
votes
0answers
16 views

Type 1 pairings and encoding function from $\mathbb G_T$ to $\mathbb G$

Let $e : \mathbb G \times \mathbb G \to \mathbb G_T$ be a Type 1 bilinear pairing. Is it possible to define an encoding function $E : \mathbb G_T \to \mathbb G$? If so, how could this encoding ...
1
vote
2answers
142 views

Sharing a secret key between many users

I would like to know if there is any security issue in sharing a secret key (of an asymmetric cryptography) between several users. I know that this secret key is no longer "secret", so it's no longer ...
0
votes
0answers
31 views

Bilinear pairing arithmetic - cryptographic accumulators

For calculating accumulated values for set of elements chosen randomly from say $ { e_1 ,e_2,...e_n}\varepsilon X $ we use the formula $acc= g^{f(e,s)}$ where $ f(e,s)= (e_1+s)(e_2+s).....(e_n+s)$ ...
0
votes
1answer
65 views

What is the difference between H(M) and H3(M, s, IDA)? [on hold]

What is the difference between H(M) and H3(M, s, IDA)? I am aware of Hash function with a Message and a Key, but there are three parameters in: H3(M, s, IDA). Here M is the message, s is the key, ...
2
votes
1answer
21 views

Are covert and rational adversaries same?

Aumann and Lindell defined covert adversaries in 2009 which is informally adversaries which have a epsilon-deterrence to cheat. Some authors (for ex. John R. Wallrabenstein) have defined similar ...
0
votes
1answer
34 views

PGP public RSA key format

I have been trying to use Go (I could post the code, but I think I posted enough already...) to generate a PGP RSA key. However every time I try to encrypt something with it, something fails. However, ...
0
votes
0answers
38 views

How can I tell how a text was encrypted? [on hold]

How can I tell what encryption method was used to encrypt this text below? I noticed this sequence repeats "C04D57B02B2B61C4", could that be a hint? It also has leading zeroes, does that point to any ...
2
votes
0answers
44 views

Cryptographic enforcement schemes using Diffie-Hellman

If one wants to set up a decentralized cryptographic enforcement scheme in which the level of 'confidentiality' of information is marked by its position in a poset, why not use Diffie-Hellman to ...
-2
votes
1answer
71 views

Would this be a plausible authenticated encryption scheme using nested encryption?

[This is was the most promising out of an incrementally developed set of (mostly flawed, to some degree) schemes I posted here, but I was told I should post each one separately] This scheme is highly ...
0
votes
0answers
32 views

Ring signatures in ECC

Are ring signatures possible with elliptic curves? If so how. The original paper by Rivest, Shamir, Tauman seems to require an invertible trapdoor function. But I've only seen algorithms for secret ...
0
votes
0answers
27 views

How many bits of entropy can I expect from /dev/urandom in iOS?

Apple's latest security documentation indicates that it now uses CTR_DRBG for generating pseudo-random numbers (previously Yarrow instead of CTR_DRBG), using "timing variations during boot" and ...
0
votes
0answers
32 views

Discrete log in Galois Extension Field

I was reading 'Pinocchio Coin' paper by Danezis et al. where they have said, "If we use the efficient pairing groups of Pinocchio, computing discrete logarithms in the exponent field $\mathbb{F}_p$ ...
0
votes
1answer
77 views

Finding public exponent e

I'm trying to create an algorithm to find the public exponent e given a plain (non-CRT) private key that doesn't include the public exponent, i.e. I've only got $n$ and $d$. A question has already ...
0
votes
1answer
28 views

How to calculate RSA CRT parameters from public key and private exponent

Given the public key (n, e) and private exponent (d), how to calculate CRT parameters (p, q, dP, dQ, and qInv) of this RSA key pair?
0
votes
2answers
77 views

Is it practical to use a stream cipher in a block cipher mode?

My idea is to use a stream cipher encrypting 16 bytes at a time as a primative block cipher in a mode of operation such as CBC mode. Is this practical or useful in any way?
-2
votes
0answers
27 views

Why don't we have hardware generate NON-pseudo, but REAL random numbers from meta-stable flip-flops? [on hold]

Software pseudo-random numbers can always be cracked because they are based on a seed and therefore deterministic. Therefore, why depend on anything that's deterministic for security? The only real ...
0
votes
0answers
17 views

public key for encrypting and both private and group key for decrypting [on hold]

A document is ecncrypted using publickey within a group(consists of many users with single public key and individual private key),then how to decrypt the document by using both public key and private ...
0
votes
0answers
58 views

Name of this attack?

I am studying Merkle tree signature. Let $\sigma=(s,Y_s,\sigma_{\text{OTS}},As)$ be a signature of certain document. Here $s$ is the index of leaf, $Y_s$ is the respectively OTS public key and $A_s$ ...
0
votes
1answer
46 views

Using ECB as encryption mode, but encrypted messages are unique

As I understand, ECB should not be used as encryption mode unless you are encrypting single blocks of data which are always unique and only are encrypted once. I have a collection of ids represented ...
0
votes
1answer
30 views

Are pseudorandom permutation really permutation in mathematical sense?

In security, and specifically Block Cipher (AES, DES, etc), when we talk about pseudo random permutations, is the term "permutation" refer to the same meaning as in discrete mathematics. That is, the ...
0
votes
0answers
25 views

Can you find the search space? [duplicate]

Let A is a random number and has 512 bits.we make B from A and B has 1024 bits.Process of B is following: C=f(A) that f is hash and C has 160 bits.Then C pass in a parallel manner 7 different hash ...

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