# All Questions

146 views

### Tamper-evident audit logs

I want to be able to detect tampering in a log file that is under the control of an untrusted party. I am not interested in secrecy, only the integrity of the contents in the file - so I want to ...
49 views

### Asymptotic Hash Function and Concrete Hash Function

I'm reading Collision-Resistant Hashing: Towards Making UOWHFs Practical, and they say that its formalization is non-asymptotic. Why is the formalization non-asymptotic? What is an example of hash ...
206 views

### XOR cipher Pseudo-random key strength

When implementing a XOR cipher with a pseudo-random key equal in length to the plaintext, Is there a significant difference in potential key strength between keys drawn from a pool of either 1000 or ...
87 views

### Biometric authentication [closed]

I see in some “Authentication schemes with biometric” papers that those authors wrote a phase as password and biometric update phase. My question is that why we may needs biometric update phase? Is ...
125 views

### What is the difference between various modes in FPE?

Format preserving encryption has three modes FE1( FFX) , FE2(VAES) , FE3(BPS) . All of them are based on Feistel Networks .Can somebody explain how they differ from each other ?
63 views

### Hash of multiset of values, which lets me compute the hash of the union

Cryptographic hash functions normally take as input a bitstring. I am looking for a hash function that takes as input a finite multiset of values. In other words, given $S \subset \{0,1\}^*$, I want ...
151 views

### DSA generate signature and verify

I'm trying to generate a signature for DSA with the following parameters: $p = 23$ , $q = 11$ , $g = 3$ , $H(m) = 8$ , $x = 5$ for the life of me, I cannot choose a random $k$ ($0 > k > q$) ...
134 views

### Is AES a linear hash?

So, having read a variety of documentations on AES encryption, I came to the unknowledgeable conclusion that the key schedule applied to the array of chunks, and not just the 14 cycles on a single ...
73 views

Assume that sender and recipient both already have each others public keys(certificates). Sender needs to generate session key to encrypt some data and sends encrypted data to recipient. All offline - ...
58 views

On page 11, definition 2 of "Simultaneous Hardcore Bits and Cryptography Against Memory Attacks", the paper outlines the following steps (PK,SK) public key and secret key are generated by defender ...
98 views

### Create a field in PBC

Edited (I removed the emphasize on Integers): My question is partly cryptography and partly programming, I would appreciate any help on any aspect of it :) I want to use PBC library to do the ...
76 views

### Different patterns of different paterns, wildcard [closed]

I'm not realy experienced with programming and such but I am wondering if the following could be implemented in, lets say, python we have the following ciphertext sequence ...
84 views

### Best hash size for hash trees

I want to know if having a 8-byte hash value is better than 16-byte hash value for use within hash trees. My mind tells me that the shorter the hash value, the better. But doesn't a smaller hash ...
184 views

### How is SSL secure from rogue Certificate Authorities?

There's one thing that I've never quite understood about SSL (which perhaps means I don't understand SSL at all): how is SSL secure from rogue Certificate Authorities? This is probably best ...
78 views

We're building a data service that is expected to go out through a single "fat pipe" channel. The design requirement says that the data in the channel must be protected by authentication and ...
85 views

### Sematically Secure McEliece

I am read the Lemma 2 (pp13) in the paper "Kazukuni Kobara and Hideki Imai: Semantically Secure McEliece Public-Key Cryptosystems –Conversions for McEliece PKC– (PKC 2001)". Related to the question ...
162 views

### RSA - Ecrypting the same data with the same public key = same ciphertext?

If an adversary knows my public key and guesses what was my plaintext, can he test for it somehow? The most obvious way is encrypting the guessed plaintext with my public key and the same parameters ...
68 views

### PBKDF2 when dkLen and hLen have the same size

I was reading RFC 2898 and something is not clear to me. When I use PBKDF2 with SHA-256 and I want a derived key with length 32 bytes (the same length as my hash function output), your derived key ...
62 views

22 views

### New to Cryptography [on hold]

A friend of mind asked me if I could take a crack at this here: PRSAO EGERA UIADM WEHDN ISNRA SAWUA AESSR EFGDO SOGVO RBEEE AARTE SCTDF MENUI BRTTL MEYTU MTMEU AIKWH UTKWE RWAHM NPWRA EESON ONESE ...
20 views

### Crypto (mainly binary [on hold]

So I have this binary data, and I am not really sure where to even start with decrypting it... I ran it through python's binascii library (b2a_uu, b2a_hex, b2a_qp) and I haven't gotten even a place to ...
28 views

### Is there any probabilistic version of RSA?

I have now studying the RSA, but I think that is it possible to have some probabilistic version like a random bit string "r" XORed with the key? Is there any probabilistic version of RSA? Thak you ...
33 views

### How to compute 3P from elliptic curve where P is (28, 8) [on hold]

Consider the elliptic curve E31(1,1): Calculate 3P, where P = (28,8).
15 views

### Smart card minidriver: CryptAcquireContext failed with error 0x80090016 (NTE_BAD_KEYSET) [on hold]

I encountered a problem just like: https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/838037c5-2480-4ffd-8524-c8c2b16c620c/minidrivers-problem-in-windows-7?forum=windowssecurity I wrote a ...
13 views

### Computing the redundancy of language for a Vigenère cipher with m=5

Redundancy of L = 1- Entropy of L/ log base 2 {P} The Redundancy of L is given by 1 minus the Entropy of L divided by log base 2 of the Cardinality of the Plaintext space. Could someone advise me how ...
45 views

### Proof that counter mode of operation and CBC mode are CPA secure when pseudorandom permutations?

I know counter mode can be CPA secure, when used with block ciphers modeled as random permutations. If we use pseudo-random permutations, is it still CPA secure? Is there a proof? How about CBC ...
17 views

### Verify signed file using GPG by passing in signature hosted online rather than stored locally (i.e. in keyring)? [migrated]

Is it possible to pass the URL of a GnuPG signature when executing a verify query against a signed file? For example, instead of: gpg --verify file.txt Is there ...
26 views

### Arranging Vigenere Cipher into columns [migrated]

As I understand if you arrange a Vigenere cipher into columns you can use the Index Of Coincidence to find out the key length. I'm struggling to write an Algorithm that would take a piece of text and ...
60 views

### How can I break this cipher? [closed]

I am currently trying to break: +VZ7ZVcKPavGh4iGArNy and +VZyY1sBOazFh4COBrB2 I have a known plaintext that is: 378734493671000 which encrypts to: +VZyZlAHP6HAgoaPBrBz Is anyone able to explain how ...
53 views

### initiate the elliptic curve

when we consider a curve in a prime field for example Weierstrass form and want to initiate it in Miracl,we should give these inputs for initiate curve: ebrick_init(&binst,x,y,a,b,n,window,nb) ...
54 views

### Existential Unforgeability of signature scheme against Adaptive Chosen Message Attack

While reading a literature on signature schemes, I came across the concept of Existential Unforgeability of signature scheme against Adaptive Chosen Message Attack. Can anyone point me to the paper ...
57 views

### I need to know number of encryption/decryption operations?

If i want to break quadruple DES (say EDED), what is complexity? Like for EDE, it is O(2^112).
51 views

### How would I write my own asymmetric encryption algorithm (not RSA, DES etc)? [closed]

I am looking for some advise on how to go about writing my own asymmetric encryption algorithm. It does not by any means need to be as secure as the commercially available algorithms (RSA etc), it is ...