# All Questions

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### Weak and Strong Collision Resistance, again

Weak collision resistance (CR), or second-preimage resistance, is the property that given $x$ and $h(x)$ ($h$ a hash function) it's difficult to find $x' \neq x$ such that $h(x') = h(x)$. Strong CR, ...
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### Is it possible to brute force a single smaller variable in $\operatorname{HMAC-SHA512}(k, a\ ||\ b\ ||\ c\ ||\ d)$?

Given $c' = \operatorname{HMACSHA512}(k, a\ ||\ b\ ||\ c\ ||\ d)$ and the 32-bit integers $a$, $b$, $c$, and $d$ is it feasible to alter $b$ and produce a valid MAC under the unknown key? I ...
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### reconstructing data on a noisy channel?

I have an interesting situation where I have a block cipher and a noisy channel. The interesting thing is that I happen to know much about the data. The cipher is a balanced Feistel network, and for ...
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### Client Puzzles and HMAC

I'm learning about client puzzles for DoS (Denial of Services) Protection, and I came across this question. For each request, the server sends the client a freshly generated random challenge r and ...
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### How does the math part of RSA work? [duplicate]

I understand the theoretical part of RSA (the concept of public and private keys), but I don't understand the mathematical part. Can anyone please explain it to me in simple terms? Thanks.
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### Government root SSL certificate possible vulnerabilities [closed]

I'm writing an article about new government law in Kazakhstan. The law was accepted in December, but now one of our providers announced information for small and medium business how to install ...
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### Affine Cipher - Greatest Common Divisor

Really simple question regarding the Affine Cipher. Can someone tell me how $3^{-1}$ is supposed to result in 9 in the following explanation below?
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### Differential bound of the S-Box in GOST R34.11-2012

In Russian GOST R34.11-2012 LPS-transformation is used. LPS gets all of its non-linearity from the 8-bit S-box S, which apparently has been designed to offer resistance against classical methods of ...
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### Cube-Root attack - RSA with low exponent

I have this RSA public key ...
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### Understanding Hellman's TMTO

I am trying to understand the basic TMTO by Diffie Hellman as described here. I am having trouble understanding this passage here: Hellman had the idea of storing the dictionary in the form of ...
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### How were the diffusion statistics for norx calculated?

I was reading the norx specification and came across this section, which provides some kind of statistics about the diffusion of the norx round function. However, I don't see how these values were ...
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### HMAC-SHA1 vs. AES

This might be a very silly question, but I am a total novice in encryption. I don't know where to start searching for an answer to this problem. I am building applications using a proprietary ...
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### VIC cipher author known?

Does anybody know if the design of VIC cipher is attributed to anybody? I've tried Google and found nothing. There are quite a few sites describing the method in detail, a few implementing it ...
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### How common are weak RSA keys?

There exist certain attacks that can be used against RSA keys whose prime factors are of specific forms, such as one by Coppersmith. How common are these RSA keys? If you generate primes randomly, ...
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### Are developers expected to implement Diffie-Hellman key exchange themselves?

I noticed that the GO standard library has some really nice functions for performing AES encryption / decryption in various modes. However, I couldn't (yet) find anything for Diffie-Hellman key ...
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### Are CSPRNGs quantum-resistant?

It's fairly well known that Shor's algorithm kills RSA, DSA, ECDSA, DH, ... and that symmetric ciphers (AES and 3DES) and hashes (SHA-2, SHA-3) are safe as long as you double your key size / output ...
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### Problem with braking SASAS type of encryptions

I am reading the paper Structural cryptanalysis of SASAS. I understood it till the section Recovering of layers S1 and S3 on page 6. However because of my limited understanding of mathematics, I am ...
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### IX509Extension XCN encoding?

I understand from reading MSDN that the X509 v3 extensions must be handcrafted. This involves the CRL, AIA, name and policy constraints, policy mapping, private key usage period, and subject ...
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### Certificateless cryptography Implementation

Hello guys I am trying to implement Certificateless Cryptography algorithm with reference to this base paper. Right now I am trying to implement the code in java. ...
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### is it possible to reverse engineer the key on a AES-256 encryption? [duplicate]

If I have the original text and the encrypted one, is it possible to reverse engineer the key? And more importantly is it doable ? I tryed to look up the algorithm but i'm way too rusted and with no ...
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### Difference between AES-CCM and AES-CCM*

I'm trying to understand the different between AES-CCM and AES-CCM* (as defined in IEEE Std 802.15.4™‐2011, Annex B). I see that there are more restrictions on L and M and also M=0 is allowed: L = 2 ...
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### Is it possible to create a detection oracle for all block cipher modes? — ciphertext-only cryptanalysis

I have made an ECB/CBC detection oracle, and am now trying to make a detection oracle that can differentiate between CBC/CFB/OFB/CTR/etc. I can already tell ECB apart from the others due to this ...
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### timing attack ecdsa scenario in software implementation

Timing attack ecdsa in software with standalone program is it possible? There is paper discuss timing attack ecc in client server scenario in openssl,but i still dont understand it. Any body can ...