-1
votes
2answers
998 views

How does the rand() function in C work? [closed]

I want to know how rand() works (even when I don't provide any seed how it produces PRNs?) thanks!
-1
votes
2answers
206 views

What are alternatives to the random oracle model for modelling hash functions? [closed]

I was looking for more realistic alternatives to the ROM for describing hash functions in theoretical proofs. I came across the common reference string model (where hash functions can be modeled as ...
-1
votes
1answer
134 views

Cryptographic Primitive Method

Is there any cryptographic primitive bijective (one-to-one and onto) function for creating cryptographic tools like symmetric encryption/decryption, Hash code generator, MAC, HMAC and Random number ...
-1
votes
1answer
47 views

Prove that the affine cipher over Z26 has perfect secrecy if every key is used with equal probability of 1/312

Prove that the affine cipher over Z26 has perfect secrecy if every key is used with equal probability of 1/312. Just some guidance/help with this problem would be greatly appreciated not sure how to ...
-1
votes
1answer
44 views

How to use the key from a Diffie Hellman exchange? [closed]

I watched a YouTube video about Diffie-Hellman called "Diffie-Hellman Key Exchange", and it said after doing some modulo operations with the public modulus and generator and the random private ...
-1
votes
1answer
71 views

Block Cipher Modes

I have a question here asking the following: Why do block ciphers need the use of blocking modes? To encrypt messages larger than the size of the block. To avoid having the same block ...
-1
votes
1answer
154 views

RSA given q, p and e?

I am given the q, p, and e values for an RSA key, along with an encrypted message. Here are ...
-1
votes
1answer
45 views

Witness and Commitment in Commitment schemes [closed]

In connection to a commitment scheme, how are witness and commitment different? Are 'Binding' and 'Hiding' properties defined w.r.t. witness and commitment or both?
-1
votes
2answers
70 views

Vigenere ciphertext encrypted with another vigenere cipher

I have been learning about Vigenere ciphers and then thought of this scenario: if a cryptographer encrypts a plaintext English message with a Vigenere cipher and then another cryptographer, who wants ...
-1
votes
1answer
38 views

Hash function and indifferentiability [closed]

What are the properties derived from the fact that a hash function is indifferentiable from a random oracle?
-1
votes
1answer
93 views

What's the best packet cipher mode for use with UDP for example? Advantages or disadvantages of any alternatives?

Cipher modes typically assume data is streamed or read from a reliable channel with guaranteed ordering. However, many communication transports, such as UDP, are not reliable and don't guarantee order ...
-1
votes
1answer
62 views

I am new to Cryptography and I wonder if one can Suggest me Beginner Projects [closed]

Sorry for this kind of a question, but I really like to learn and improve in cryptography. At the moment I am following online lectures from https://class.coursera.org/crypto-011 , can anyone suggest ...
-1
votes
1answer
91 views

Questions on FHE over the Integers - the question modified!

I modified my question since it is not as specific as I wanted. I'm studying FHE over the Integer which is https://eprint.iacr.org/2009/616.pdf I got questions about the proof of Lemma A.1. In page ...
-1
votes
1answer
54 views

PGP message integrity : How can receiver of an email check the integrity using the sender's public key?

PGP message integrity: Basically, only private key can decrypt message encrypted with public key. But in the message integrity service in PGP does the reverse, where the Hash of the message if ...
-1
votes
1answer
70 views

Pseudo Random Generator with fixed Hamming Weight [closed]

I'm searching for way to generate secure pseudo random sequence with a fixed Hamming weight using a seed. I found below code but I need a seed to generate a sequence ... (and need know if is possible ...
-1
votes
1answer
113 views

How Does Progressive Hashing Work?

Example: http://jsfiddle.net/KGtUE/ https://code.google.com/p/crypto-js/#Progressive_Hashing sha256.update("abc"); sha256.update("def"); sha256.update("ghi"); ...
-1
votes
1answer
55 views

How small are we talking about when defining the small public/private key exponent [duplicate]

I've been wondering about the 'small' part of the attacks on RSA, like the small public key exponent and the small private key exponent and what's not really clear is how small are we talking about? ...
-1
votes
1answer
120 views

Reverse engineering a single checksum byte [closed]

I am working to understand a system which saves a few bytes of data together with what appears to be a single checksum byte that provides a very naive guarantee that the data has not been tampered ...
-1
votes
1answer
60 views

How can the key size be calculated [closed]

If the decrypting key is 448, then what is the key size? Suppose I am encrypting a plain text with a key by choosing some random numbers between ...
-1
votes
1answer
124 views

PRG existance and P versus NP

how can we prove that if there is a secure PRG then P!=NP or in reverse order?(is there any reduction?) a secure PRG is a pseudo random generator that for every eficient (running in probabilistic ...
-1
votes
1answer
85 views

Symmetry for finite cyclic groups (Z/pZ)∗

How well is it known that for $i$ such that $1 \leq i \leq \frac{p − 1}2$: $$ g^{i+(p−1)/2} = g^{i−1+(p−1)/2} − g^i + g^{i−1} \pmod p $$ Whilst working in the finite cyclic group of prime moduli ...
-1
votes
1answer
238 views

How can I convert numbers into prime numbers?

I'm working with one-way accumulators, but I'm not knowledgable in cryptography. Is there an easy peasy way to hash numbers (or whatever) into prime numbers? Obviously I'd like it to be collision ...
-1
votes
1answer
51 views

Positioning of keys in encrypted text

I'm just looking at very simple encryption. I've noticed that the key is typically either at the front or at the back of the encrypted text. This is quite easy to break if you know the key. It can ...
-1
votes
1answer
67 views

encrypting data signals using the time variations between two independent coupling functions [closed]

There was a recent article about a new encryption technique that encrypts "using the time variations between two independent coupling functions". What is this technique they are referring to?
-1
votes
1answer
80 views

How to create PSK key? [closed]

I'd like to create a PSK key to use with TLS-RSA-PSK-WITH-AES-256-CBC-SHA - what is the format of this key?
-1
votes
1answer
144 views

Hash Based Encryption (fast & simple), how well would this compare to AES? [duplicate]

First of all, I know it's a very bad idea to invent your own encryption algorithm. It's better to use existing known, trusted, extensively tested and studied algorithms with a proven track record. The ...
-1
votes
1answer
184 views

Number of possible keys in a Play fair cipher [duplicate]

So for the play fair case, the number of possible keys is : 26x26 = 676 possible keys But if we consider the repeated letters, how many unique keys will the play fair have? I mean how will ...
-1
votes
1answer
67 views

Adding “salt” to “doHash” function in Java [closed]

For one of my university projects I am being asked to "Improve the code to satisfy the pre-image resistance requirement." Basically the program is a basic encryption server system, and when I type a ...
-1
votes
2answers
109 views

Need Help Reversing my Encryption Algorithm [closed]

So I wrote a simple encryption algorithm (Not very secure, just a starting point. I don't want criticism on it.) and I have been having trouble finding a way to decrypt the text. The algorithm is here ...
-1
votes
1answer
118 views

How to determine which type of crypto is used in a text file? [closed]

is there a tool or a way to determine which type of crypto is used in this type of text: ...
-1
votes
1answer
120 views

Are the protocols DH-EKE, B-SPEKE, A-EKE, and SRP are considered challenge-response authenticaion mechanisms? [closed]

I got confused which one is considered challenge-response mechanism which one is not.
-1
votes
1answer
359 views

why RSA uses Semiprime numbers? [duplicate]

Why does RSA use semiprime numbers? Why not just use any big number ?? What is the advantage of the two original numbers being prime? Because factoring any big number will be difficult
-1
votes
1answer
95 views

Use of Different keys with PCBC

Currently I am having a doubt, while making a "DES PCBC" encryption on an image I observe a bit of the silhouette of the image (Probably because of the XOR between plaintext blocks and ciphertext ones ...
-1
votes
1answer
78 views

Paillier Crypto System : Pros and Cons? [closed]

Can you please list the pros and cons of the Paillier crypto system you have encountered or found?
-1
votes
1answer
103 views

Can someone explain how this unpadded RSA formula works?

Taken from http://en.wikipedia.org/wiki/Homomorphic_encryption, $\mathcal{E}(x_1) \cdot \mathcal{E}(x_2) = x_1^e x_2^e$ $\bmod\; m = (x_1x_2)^e \;$ $\bmod\; m = \mathcal{E}(x_1 \cdot x_2)$ What is ...
-1
votes
1answer
72 views

Is size Q equal to size SHA(Q)? [closed]

Assume d is a 128 bit random integer and P is base point of an elliptic curve and Q = dP is a point on the elliptic curve and SHA is a hash function with 128 bit output, my question is: Is size Q ...
-1
votes
1answer
70 views

The specification of modern, non-communicating cipher machinery [closed]

I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed. Consider powerful electronic machinery which remains in the custody of communicating ...
-1
votes
1answer
1k views

AES: keylength and password length? [closed]

What is the difference between the keylength and the length of a password for AES-256?
-1
votes
1answer
162 views

Integer factorization via geometric mean problem

presume: we have A and B integers, and C - product of multiplication of A and B, A and B are prime numbers (strong or usual) G - is geometric mean of A and B (square root of C) also, we have: if B > ...
-1
votes
1answer
136 views

Which areas in CS will be (or have been) most affected by fully homomorphic cryptography? [closed]

I'm in the middle of planning a 5000ish word essay on fully homomorphic cryptography, the current practical implementations and their limitations. Which areas of CS as a subject have been (or will ...
-1
votes
2answers
319 views

Is triple des similiar to RSA in that they message size is limited to the key size?

Is triple des similiar to rsa in that the message size you can encrypt is limited (unlike AES)? Yes you can break the message size into parts and apply it, but I'm not interested in doing that so I ...
-1
votes
2answers
75 views

Book Didactic Security Notions [closed]

I want study more about cryptography reading papers, but I have a problems to understand few concepts: security notions, random oracle model, IND-CCA, ... etc. I began study this concepts by internet: ...
-1
votes
1answer
133 views

Obtaining a key that's using ice algorithm

I have a text file that has been processed by the SNOW steganography tool that uses ICE encryption. However, I do not know the key that would enable me to decrypt and retrieve the message hidden. ...
-1
votes
1answer
66 views

construct an election protocol for the following election problem..? [closed]

I am something new to election protocols and I am trying to construct an election protocol for the following problem: Let $A= \lbrace a_{1} , . . . , a_{n} \rbrace $ and $B = \lbrace b_{1} , . . . , ...
-1
votes
1answer
397 views

File Encryption/Decryption in ECB mode [duplicate]

Possible Duplicate: Removing Padded Value in Decrypted Message I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't ...
-1
votes
1answer
44 views

What's algorithm encryption ?Twofish or AES [on hold]

I have one ciphertext but i do not know algorithm it . i know it's AES or Twofish what are your suggestions ?
-1
votes
0answers
44 views

How do you perform frequency analysis to break Vigenere cipher programmatically?

I am trying to write a program to which when provided a ciphertext(maxlength - 200) and a key length(maxlength - 40), gives a plaintext as output from a possible set of plaintexts. By possible set of ...
-1
votes
0answers
63 views

Decryption of .png and .jpg files [on hold]

I'm trying to modify graphic assets of the software I'm using (for aesthetic puroposess, I guess it's hard to do something harmful with graphic assets) but developer encrypted them. I'm not sure why ...
-1
votes
0answers
30 views

Side channel vulnerabilities in SW RSA implementations? [closed]

I would like to know a list of practical side channel attacks with references. These attacks should work on SW implementations and I do not consider attacks that require physical access such as power ...
-1
votes
0answers
45 views

Create collision examples with MD5 hash with salt

I'm using the following lines to create a hashed string String source = String.format(%s %s %s", salt, firstPart, secondPart); byte[] bytes = md5(source); ...

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