# All Questions

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### PBKDF2 for login key, scrypt for encryption key

I need to derive two keys from a single password client side. One for in-browser login, the other for encryption. Is the following secure ? ...
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### LUKS multiple key slots - what's the intuition?

LUKS volumes have the ability to allow multiple independently usable passwords, as explained here: [https://code.google.com/p/cryptsetup/wiki/FrequentlyAskedQuestions] The intuition behind basic ...
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### Crypto hash function vs encryption algorithms

Why is a cryptographic hash function generally faster to execute in software than conventional encryption algorithms such as DES?
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### IV's for different AES encryption modes

I wanted to know if my understanding is correct! I have been reading up on aes encryption and modes(specifically CTR and CBC) and it took me sometime to understand the concept of IV. If the IV is ...
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### Large file validation on an embedded system through hash and encryption

As a preface, I have to say that I am a noob in this area. Having said that, I will ask the question. I have a situation where I need to validate and protect against tampering a handful of large ...
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### Implementation of garbled circuits using RSA

I was just reading these notes on garbled (Yao) circuits and I just stuck trying to figure out how an implementation of Table 1 would work using RSA encryption. In RSA the public key is (n,e). So for ...
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### Serpent 256bit key wrong round keys

Assume that we have this 256bit key: 15FC0D48 D7F8199C BE399183 4D96F327 10000000 00000000 00000000 On first 0-7 keys we can't apply formula wi=(wi-8 xor wi-5 xor wi-3 xor wi-1 xor phi xor i)<<&...
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### Generation of N bit prime numbers -> what is the actual range?

Short version: When generating a prime number of N bits, should I draw random numbers from the range $[0 , 2^n]$, or $[2^{(n-1)} , 2^n]$? Context: I'm trying to implement a toy-version of RSA as a ...
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Groth-Sahai framework enables us to commit to QE, MSME, PP equations. Now, is the equation below committable in GS framework? A bilinear map $e: G_1 \times G_2 \rightarrow G_T$. $g_1 \in G_1$ and $... 1answer 484 views ### VKO GOST R 34.10-2001 (described in RFC4357), Key Agreement Algorithm. Looking for its implementation/detailed description/examples VKO GOST R 34.10-2001 was described in RFC4357 Page 7 But the description is very poor. Here it is: This algorithm creates a key encryption key (KEK) using 64 bit UKM, the sender's private key, ... 1answer 139 views ### Help to understand the chameleon hash function? Recently, I'm reading Non-Interactive Key Exchange, in the section 4.2(Towards a factoring-based scheme in the standard model,Page 10), the authors uses$$t\gets ChamH_{hk}(Z||ID;r);\\ Y\gets ... 2answers 283 views ### How can I map arbitrary group elements to unique integers without using Hash functions? Let's say, I have a group$G$of large prime order$p$. A set$S$consists of$n$random elements chosen from$G$. Without using a collision resistant hash function$H$, how can I map elements of$G$... 2answers 1k views ### SHA512withRSA - Looking for details about the Signature Algorithm I am trying to find information about the Signature Algorithm SHA512withRSA and have been unsuccessful so far. In the current state, the signature is too long, so I would like to check the code for ... 1answer 133 views ### Generating S boxes that satisfy Coppersmith's criteria? I'd like to generate all possible 6-bit to 4-bit S-Boxes that satisfy the criteria for S-Box design given by Coppersmith, but I have a few doubts: How many such S-Boxes are possible? Is there any ... 1answer 167 views ### Bit padding instead of PKCS#5 padding Padding oracle attacks are a huge nuisance when using CBC mode encryption without authentication. Wouldn't all those padding oracle attacks be avoided if we'd just use bit padding instead? Or is does ... 1answer 204 views ### Is multiple encryption using NaCL and TLS better? In general, the idea of multiple encryption sounds interesting - for creating stronger cyphers (especially against implementation bugs), one could always get the configuration details wrong and mess ... 1answer 332 views ### Prevent MITM attack while encrypting data by using ElGamal ECC? I am using ElGamal ECC to encrypt my plain text data. I want to ensure that my data is safe from a Man-In-The-Middle attack. What methodology I can adopt to achieve this goal? How can we prevent a ... 1answer 106 views ### How can finding a collision help an attacker with tampering messages with HMAC As stated in the HMAC RFC (RFC 2104): The strongest attack known against HMAC is based on the frequency of collisions for the hash function H. How can a collision benefit an attacker? I would ... 1answer 236 views ### PBKDF2-SHA256+SHA256 for password storage I recently came across an interesting paper detailing the use of hardened session cookies. Each cookie includes a preimage of the password hash, and the preimage is hashed once more and compared to ... 1answer 123 views ### Encryption method with master key and user keys I am working on a concept for a game that in the end will allow data sharing via plain text, but I would like to give the user the option of encrypting the data so that other players cannot modify it, ... 1answer 125 views ### Construct block cipher from a smaller one with mixing function I read about the AEZ encryption scheme as presented at the CAESAR competition. To me it seems like a construction of an arbitrary length block cipher from a smaller one. The key component is the ... 1answer 120 views ### Cryptanalysis of Nonlinear Table Lookup I am trying to derive a symmetric key based on a master key, combined with a simple string. Based on my limited knowledge, it seems that something like PBKDF2 would do that for me in a well-defined ... 1answer 225 views ### Are there any cryptographic flaws in my webhook signing process? Out of band my services have exchanged secret keys. These secret keys are then used to prevent two things of the webhooks (HTTP calls triggered by Service A to Service B when an event occurs in ... 1answer 110 views ### run length testing [closed] Looking for guidance/references with/about calculations: I am designing a widget that creates N-bit binary sequences. My customers target spec for the sequence's minimum entropy is X bits/bit. I plan ... 1answer 93 views ### Composing and Inverting Symmetric Encryption Keys Using a symmetric encryption algorithm$E$on a message$M$, users usually send$E(M)$to the recipient and then the recipient will compute$E^{-1}(E(M))=M\$ to retrieve the message. For what symmetric ...
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I'm trying to analyze a login protocol based on symmetric key cryptography. I'm just starting out, so this may very likely be a very bad idea, but nonetheless I'd like to hear your thoughts on it. ...