0
votes
3answers
237 views

Implementing a web app where the server cannot decrypt its own data?

I'm a cryptography novice, but I think that the world needs to move towards an "encrypt everything" mentality as much as possible. As a result, I've been thinking a lot about ways to build a web app ...
0
votes
2answers
117 views

Factors of RSA modulus

In the article A Method for Obtaining Digital Signatures and Public-Key Cryptosystems, the original RSA article, it is mentioned that Miller has shown that n (the modulus) can be factored using any ...
2
votes
1answer
111 views

Private Information Retrieval--Is it still theoretical?

Are there any real world products in which private information retrieval techniques are used?(a data hosting server oblivious of which data item was fetched from it?)If not what are the major barriers ...
2
votes
0answers
74 views

Key Recovery Smart-Vercauteren SWHE

In the article (https://eprint.iacr.org/2009/571.pdf, pag 8) of Smart and Vercauteren, it is mentioned that the recovery of the private key is an instance of the small principal ideal problem. But I ...
0
votes
0answers
65 views

Simplifying the zero-knowledge proof example? [duplicate]

There is this http://en.wikipedia.org/wiki/Zero-knowledge_proof#Abstract_example. Now I'm curious about this. Why is it not possible for Victor to stand at the entrance and watch Peggy take one path ...
0
votes
1answer
46 views

white-box cryptography and its applications [closed]

I am a programmer who is doing research into whitebox cryptography. What I hope to do is to use WBC for an DRM application however as some of us may know, WBC is theoretically impossible therefore I ...
1
vote
4answers
79 views

Difference between Pseudorandom Function vs randomly chosen function

I am currently going through a course in cryptography. In this, I stumbled upon Pseudorandom Functions. I got a little idea of Pseudorandom Generators which map an input string (key) to an extended ...
0
votes
0answers
26 views

How to find the factors of the modulus? [duplicate]

In the article "A Method for Obtaining Digital Signatures and Public-Key Cryptosystems", the original RSA article, it is mentioned that Miller has shown that n (the modulus) can be factored using any ...
-2
votes
0answers
51 views

If the ciphertext of Goldwasser-Micali has been falsified, what is the plaintext after decryption?

Alice encrypts 0 using Goldwasser-Micali encryption scheme and sends the ciphertext to Bob. If some bits are flipped during the transmission, what can Bob get after decrytpion. Can Bob get 1 with a ...
0
votes
0answers
8 views

Has the POODLE SSL vulnerability ever actually been used? [migrated]

Is there any evidence that the the POODLE SSL or TLS has actually been proven to be a risk for file transfer like SecureFTP etc...? ...or is it just a theoretical exposure?
1
vote
1answer
38 views

ASN.1 encoding off RSASSA-PSS default parameters

I am not totally sure the question belongs to crypto and not stackoverflow but nevertheless... The problem is the encoding of the RSASSA-PSS default algorithm identifier parameters in an X509 ...
0
votes
3answers
50 views

private keys for multiple devices [closed]

I have an architecture where: a user can have multiple devices (phones) the server needs to broadcast the payload to all devices through the same channel (basically, all devices listen and receive ...
0
votes
1answer
48 views

What is the importance of adding round key in AES

I know this may not be the place to ask this but I have found it difficult to find an answer to this question. I know the steps of the AES encryption algorithm but I am finding it difficult to ...
3
votes
1answer
199 views

Difference between Hash function and Random Oracle

Going through the blog post, I was under the impression that any cryptographic scheme which makes use of hash function is said to be using random oracle. But, I have come across one construction of ...
0
votes
1answer
36 views

Can one deduce the symmetric key size used to encrypt a given a piece of ciphertext?

Assume an attacker captures a piece of ciphertext encrypted with a symmetric key. He knows all the details of the algorithm used to encrypt except for the size of the key used in this case. Can he ...
0
votes
1answer
100 views

Key management protocol for end-to-end security on Advanced Metering Infrastructure

I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
28
votes
7answers
20k views

Taking advantage of one-time pad key reuse?

Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
0
votes
1answer
27 views

Integrity protection in wireless sensor networks [closed]

I have done a lab about wireless sensor nodes and got in touch with encryption for the very first time. There are some questions on my sheet, especially on integrity protection (the attacker wants to ...
-1
votes
1answer
48 views

Problem with implementing DES in python

i'm implementing DES in python and i've stumbled upon a problem i can't really find the problem, after debugging it i narrowed it down to this function, can anyone tell me if i'm implementing the DES ...
0
votes
1answer
31 views

Unique assignment of X.509 certificate to each client

I'm trying to implement a short scale electronic voting application in a domain comprised of no more than 100 clients. System administrator is able to create new election instances and each client is ...
0
votes
1answer
104 views

How much (home PC) CPU time is required to generate a prime number of a given size?

How much CPU time is required on a typical home computer to generate a prime number of size 100 bit, 200 bit , 512 bit and 1024 bit using given random bits of the respective sizes? Please note that ...
1
vote
1answer
69 views

Strength of RSA with OAEP

In our current system we use an encryption solution based on RSA with OAEP padding. Key size is optional but default 2048. What is the general strength of RSA with OAEP? Are there know attacks that ...
-1
votes
2answers
66 views

Is there a client-side program to cryptography a HTML page and decode if correct password is writen? [closed]

I want to know if there is an easy way to do this: create a complete HTML page cryptography the text content (image is not important) ask user some password check the password with a cryptographed ...
1
vote
1answer
46 views

What is the algorithm behind PasswordDeriveBytes?

Microsoft has created an implementation of PBKDF1 in the PasswordDeriveBytes class. It can however generate more bytes than PBKDF1, which is limited to the number ...
0
votes
1answer
54 views

What is the difficulty of DLP in GF(P^Q) with a subgroup with a prime order of L

Given a finite field GF(P^Q), having a subgroup with a prime order of L (P,Q,L are all primes), how difficult is it to find the discrete log, is it related to P and Q or is it related to L, or to ...
0
votes
1answer
49 views

Using hash of plaintext as nonce in NaCl secretbox- bad idea?

I need a nonce to encrypt my stuff using NaCl secretbox. I will be transmitting the nonce along with the ciphertext, which I have been told is OK to do. It occurs to me that one could simply use the ...
3
votes
1answer
64 views

Is changing $H(R\mathbin{\Vert}A\mathbin{\Vert}M)$ to $H(R\mathbin{\Vert}A\mathbin{\Vert}H(M))$ in EdDSA secure?

EdDSA calculates $s=(r+H(R\mathbin{\Vert}A\mathbin{\Vert}M)\cdot a)\bmod\ell$ and $r=H(h\mathbin{\Vert}M)$, with $H$ being the hash function (SHA2/512); $B$ being the generator; $A$ being the public ...
0
votes
2answers
46 views

Where are the ChaCha20 test vectors/examples?

I see in the Salsa20 specification there are test examples throughout the document to help an implementer make sure every function works as designed. Consequently the whole algorithm would work ...
0
votes
1answer
103 views

Base64 with shuffled alphabet

I have a base64 'cipher' text, I know that in clear text is a hidden xml document (I do not know nothing about its structure), but the base64 aplhabet was somehow shuffled. Is there any smart way, how ...
3
votes
1answer
98 views

Isn't the security of EC curve 25519 126 bits?

The security of the EC25519 is given as 128 bits, but since the order of the group is 252 bits shouldn't the security be 126 bits? Given as half the magnitude of the underlying field, since DLP ...
3
votes
3answers
433 views

P = NP and current cryptographic systems

I've recently heard some people claiming that if the fact that P = NP is proven, most (all?) the current cryptographic algorithm considered secure like RSA will be unusable in secure systems. My ...
-1
votes
0answers
16 views

Question about the Theta step of Keccak

In the question What criteria make the theta step of Keccak's round function reversible?, poncho said that:In the Keccak case, the actual value of z=64 is not a multiple of L(5), and hence θ is ...
0
votes
1answer
93 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance. I don't know what the key is but I know 64 byte ...
0
votes
1answer
24 views

Effect of CFB IV reuse

If an Initialization Vector (IV) is reused (under the same encryption key) in Cipher Feedback Mode (CFB), what is the effect upon security? I know there is some negative effect upon security, but I ...
1
vote
3answers
74 views

Key derivation of public key without knowledge of private key?

I'm looking for a convenient way to share a set of public keys across multiple services, while preserving privacy by preventing these services from tying the identity of these public key sets together ...
5
votes
1answer
297 views

What criteria make the theta step of Keccak's round function reversible?

From what I've been reading, Keccak's round function is reversible. That's pretty obvious for the $\rho$, $\pi$ and $\iota$ transforms. For $\chi$ to be reversible, $x$'s range has to be odd — but ...
0
votes
1answer
39 views

How to implement the Salsa20 hash function?

I am currently implementing Salsa20 from the specification as an exercise in learning and self-flagellation. I have Sections 1-7 passing the test examples provided. I am now stuck on Section 8, The ...
1
vote
1answer
122 views

Timelock puzzle improvment

I came across this question with this answer about a cryptographic timelock-puzzle that needs approximately 30 years to be solved. There is also an explanation with source code for that puzzle ...
0
votes
2answers
100 views

Is it possible to use structures other than finite fields?

I have some difficulties to understand why we are using finite fields in cryptography. Why do we use field? Why not ring or group? Is that really necessary that the field is finite? Why not real ...
0
votes
3answers
296 views

Can you help me with this Random Number Generator function?

By someone's suggestion, I am posting this question from math.stackexchange.com. I want to find out a suitable function or algorithm, which can provide a random sequence like this… Input: $3$ ...
0
votes
0answers
5 views

Point of elliptic curve [migrated]

How can we calculate the multiple of a point of an elliptic curve? For example having the elliptic curve $y^2=x^3+x^2-25x+39$ and the point $P=(21, 96)$. To find the point $6P$ is the only way to ...
1
vote
1answer
29 views

Question about key verification

I am studying for network security exam. And in the slide about Key Management, under a heading Key Verification I see this: Key Verification Almost all cryptographic algorithms have some weak keys ...
3
votes
5answers
443 views

What is the SSL private key file format?

I was researching about how to encrypt with RSA. I understood everything but not the format of the private keys. In the phpseclib (RSA in PHP), you can import your private key (private.key format) ...
0
votes
1answer
38 views

Remove padding (CBC) from decrypted text

I have a bit problem with padding. Everything goes fine when I encrypt the text BUT when I decrypt I see some extra characters. Sometime's one character sometimes more and I dont know how to remove ...
2
votes
5answers
1k views

Why is the private key generated first in public key crypto?

I'm still new to public key crypto. I'm trying to understand how it is that the private key is generated first in public key crypto? I would have expected the private and public key to be generated at ...
0
votes
1answer
122 views

Storing AES encrypted RSA private keys on a server

I'm thinking about creating an encrypted messaging web application where users create RSA key pairs, they store the public key on the server for others to see and also store an AES encrypted private ...
-1
votes
1answer
50 views

subgroup of quadratic residue

if a number is said to be a subgroup of a quadratic residue of Z∗p, can I affirm that it is a generator of a cyclic group ? ie, say i am looking for a number which is an element of order q in Z*p, ...
0
votes
1answer
77 views

CBC with a fixed or random IV

I have two probably quite naive questions: 1) Why, exactly, is it so bad to have a fixed (or predictable) IV in CBC mode? An example would be great! 2) Given 1), why is a random IV better? And if ...
-1
votes
1answer
103 views

Which block cipher mode does the experts use? [closed]

I want to know which "block cipher mode of operation" does the experts use? I don't want to use ECB or CBC because add padding and padding mess up my code. So which one does the experts use. /Thanks ...
-4
votes
1answer
33 views

Many Time Attack [closed]

How i can XOR these two cipher texts encrypted by using same key First ...

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