# All Questions

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### Decoding base64 with key

I'm working on a program that scrapes video URLs from a website. The URLs seem to be coded in base64. Here's an example: ...
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### Is there a TLS extension for generating unique IVs for AES GCM?

Since reusing IVs is death for AES GCM, it seems like using the fixed IV in the TLS connection state is a phenomenally bad idea. It wouldn't even seem to be a good idea to use the salt + counter ...
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### Message expansion in NTRU: why is it $\log_p(q)$-to-$1$?

Suppose that we are working with the original version of NTRU with parameters $(N,p,q,k,d_f,d_g,d_\phi)$. In this case we are working with the original NTRU with the digital envelope and the ...
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### Cloning limitation of PCB [on hold]

Is it possible to clone the car key remote PCB? I am not sure wether that PCB cloned can copy the program from IC.
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### What is the structure of a Server Key Exchange Message structure when using a psk identity hint?

I need to know the structure of a server key exchange message when using a psk identity hint. I know the general structure but I can't find an example of where the identity hint fits in. Thanks.
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### How to test digital signatures between two computers?

I have to test a digital signature algorithm. I have two computers, one will be signer and the other one is verifier. I implemented both of these in C++ but I do not know how to test it. Computers are ...
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### Is order of Correlation Immunity of AES S_box Zero?

I am working on AES S_box and trying to find out its properties like Correlation Immunity, Balancedness , Algebraic Degree , ANF form etc. These Papers 1, 2 give a nice definitions to above said ...
13 views

### where is ANS X9.31 used?

FIPS 186-4 mentions two standards for RSA: PKCS #1 and ANS X9.31. PKCS #1 is used with SSH, X.509, etc. What is ANS X9.31 used with? FIPS 186-4 has the following line: ANS X9.31, Digital ...
47 views

### Proof that a encrypted file has the same content as an (existing) original

Assume that Alice has a file F which she is going to send, in encrypted form, to Bob. Alice possesses F and the public encryption key K of Bob in form of an X509-certificate. She generates the file E ...
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### Camellia Key Schedule Sigmas [migrated]

Camellia uses 6 sigmas in its key schedule with values ...
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### Are there any digital signatures valid for multiple pieces of data?

Are there any digital signature algorithms that can be used to produce signatures valid for multiple pieces of data? For example: Pick a private key $k_{private}$, which has public key $k_{public}$. ...
35 views

### Does there exist an indistinguishability formal proof obfuscator?

A formal proof obfuscator is a mapping $\mathcal{O}$ such that whenever $P$ is a formal proof of a theorem $T$, then $\mathcal{O}(P)$ is a distribution of formal proofs of the same theorem $T$. An ...
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### Do the Syllae algorithm and Malaysian cipher from Rubicon exist?

In the first episode of a tv series Rubicon (exactly in 482 and 491 lines of an English subtitles) there is mentioned “Syllae algorithm” and “Malaysian cipher”. I could not find any details about ...
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### Problem when programming Schnorr signature [on hold]

I have some questions about Schnorr signature implementation. I am trying to implement it in C++. I chose private signing key x and public verification key y = g^x. I have a message M, random number ...
15 views

### How are keys stored in a .keystore file or in a .jks file? [migrated]

I would like to know what is the structure of the keys stored inside a .keystore or a .jks file? by structure I mean are the keys stored in key value pairs? how are the passwords for several keys ...
23 views

### How can I convert an image into a long hexadecimal code and vice-versa? [on hold]

Title. Characters to fill required 30 characters minimum.
84 views

### Public key decryption mathematical analogy

To clarify, I'm talking about digital-signatures, not public key encryption. When I encrypt something with a private key, then it should be decryptable with a public key, as I've understood how ...
57 views

### Applying machine learning algorithms to homomorphic encrypted data

I have a basic understanding of encryption and I got back to the topic because of an interesting site that encrypts financial data using homomorphic encryption (HE) and I would be happy for any input ...
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### what are the kind of mathematical proofs that i need to be familiarized with to understand (or do) cryptography? [on hold]

I know reductions are highly used to show that encryption schemes are secure under certain conditions, but i don´t know what other math proofs are needed. PD: English is not my native language so ...
30 views

### Using master password to encrypt and decrypt user credentials

I need a way to store third party credentials, and I want to avoid storing passwords in plain text. I can't use a hash because I will need to be able to get the raw password to log in to the third ...
34 views

### How would low-precision Gaussian sampling impact the security of BLISS?

For digital signature, I implemented BLISS in my cryptographic suite, and wrote the Gaussian sampler based on Lattice Signatures and Bimodal Gaussians. But unlike the reference implementation and ...
10 views

### ocf-linux, Splitting large buffers into chunks < MAX_DATA_LEN [migrated]

I am using ocf-linux in an openwrt application and have run into OCF CRYPTO_MAX_DATA_LEN (64K-1) and E2BIG errors in CRYPTO_AES_CBC mode. As a consequence, I need to split the input buffer into ...
70 views

### Is there a PRNG algorithm that allows to switch between states directly, not calling next()?

Basically I need a function with the following interface: getRandomBytes(uint128 seed, uint64 state, uint16 byteCount) Consecutive calls with the same seed and ...
107 views

### Is it ever safe to use encryption with compression?

In the wake of compression-based side-channel attacks like CRIME and BREACH, are there any safe ways to combine compression and encryption? The JWE Specification was finalised almost 2 years after ...
18 views

### Is there any functional encryption scheme whose key generation circuit is in NC1?

To my best of knowledge, I have kown there exists randomized encoding scheme whose encoding circuit is in $NC^1$, fully homomorphic encryption scheme whose decryption circuit is in $NC^1$, and ...
43 views

### RAR brute force cracking speed

I have been playing around with cRARk and was astonished by the low speed. On a 2015 high-end GPU (GeForce 980 ti), it took roughly 4h 50min to test all passwords composed of an 8-character prefix and ...
37 views

### Independence of answers to queries sent to a random oracle

Assume we have an algorithm which asks random oracle $\mathcal{O}$ $Q$ queries $u_1, \ldots, u_Q$. All queries are unique, $u_i \neq u_j$ for $i \neq j$. Queries $u_i$ are random variables, too. What ...
121 views

### Do I need to prove this?

I am using ABE scheme that has already proven under BDHE assumption. Here is the scheme https://eprint.iacr.org/2008/290.pdf In the key generation algorithm, I want to tie the user secret key ...
46 views

### Why is it so hard to make longer hashes?

I was reading this answer about why there is no such thing as a SHA-1024 hash: SHA-2 was built with state and word sizes to meet the security requirements on commodity computers (x86 and Alpha), ...
32 views

### How do Raptor (Fountain codes) encoding and decoding work? [on hold]

As described in this article, a Raptor code is a fountain code that encodes a message of $k$ symbols into a limitless sequence of encoding symbols, such that knowledge of any $k$ or more encoding ...
30 views

### Secure logical AND using Ishai-Sahai-Wagner Scheme

I want to try to implement a secure AND the way it was described here: https://eprint.iacr.org/2010/441.pdf It says that there are two bits a and b and that they have been split into d+1 shares. How ...
122 views

### RSA: revealing the modulus factorization by choosing a bad message

I started reading the book Cryptanalysis of RSA and its variants by M. Jason Hinek and I stumbled upon a phrase that intrigued me: plaintext messages that are relatively prime to the modulus (i....
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### When is AES chosen instead of a stream Cipher (e.g., RC4) during an SSL connection?

During an SSL handshake, the browser sends a list of cipher suites to the server, from which the server selects one option. For data encryption, two of the several possibilities for the ciphers in ...
33 views

### Homomorphic Encryption operation for regression

I must be missing something, and I am sorry if this is a novice question... I have seen in places (eg. https://crypto.stanford.edu/~dwu4/talks/SecurityLunch0214.pdf page 13) that linear regression is ...
973 views

### Do I really need to use the same private/public key pair in RSA?

So I'm making an Android application, I need my application to be only able to scan my own generated QR codes, and I want to make sure that nobody else can generate fake ones. The data isn't ...
39 views

### ED25519 and hierarchical deterministic wallet

I'm building a solution based on the stellar codebase and using the ED25519 curve for the signatures. One of the features I've been adding to the system is a support for hierarchical deterministic ...
61 views

### Replacing signer with simulator

Assume we can prove security of digital signature scheme against key-only (no message) attacks. Now we want to prove security against adaptive chosen message attack. We use random oracle model. The ...
33 views

### Acceptable condition for dictionary search

I am trying to write a program to break transposition cipher using dictionary search. But I cannot understand the finishing condition of the search. Is there any theory that the maximum number of ...
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### Is manually 'salting' my passwords a safe alternative to having a different password for each site? [duplicate]

It is highly recommended to use a different password for each site to prevent the breach of security of one site from compromising the user accounts on all other websites that have the same username - ...