Implementing a cipher or protocol is the process of taking it from its mathematical or algorithmic description and producing a working version, often in computer software or hardware. This tag should be used for any question discussing the various potential considerations and pitfalls of this ...

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How to convert AES to a PRNG in order to run NIST Statistical Test Suite?

I want to run statistical tests on my implementation of AES. How should I convert it into a PRNG? Is there a standard way to go about doing this? I could not find much information about this although ...
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228 views

MARS and RC6 in CUDA

I am working on a project where I am benchmarking the 5 AES finalists (Rijndael, Twofish, Serpent, MARS and RC6) on CUDA Hardware. My problem is that I am no experienced CUDA programmer. My approach ...
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2answers
2k views

Why is SRP not widely used?

SRP seems to be a very good password authentication protocol, compared to any other things used now. So why is there no popular implementations, or even no working secure implementations? I tried to ...
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1k views

Are there any MGF1 and OS2IP functions available in C?

I need MGF1 and OS2IP functions, as defined in the PKCS #1 v2.1: RSA Cryptography Standard. Is there anything available in OpenSSL, or any other open C library?
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124 views

Which attacks are possible against raw/textbook elliptic curve?

A quick question, we know that raw RSA is a no go. To solve this we have different PKCS standards forcing structure on the input messages. For EC the story is something else. For signatures we have ...
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1k views

Should the secret key of Shamir's secret-sharing algorithm be interpreted byte by byte?

Should the secret message of Shamir's secret-sharing algorithm be interpreted and processed byte by byte? Interpreting it byte by byte makes it easier to process, but in case one of the shareholders ...
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83 views

How do Käsper and Schwabe's Bitsliced AES Mixcolumns work?

The only way I see it possible to do the matrix-multiplication in the MixColumns operation of AES is by shifting the bits in the multiplied number, and then reduce with the polynomial if needed. ...
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79 views

Choice of the one-way function (OWF) for Lamport signatures

I am studying the Lamport signature scheme, and I found that in many sources (eg: Hash-based Digital Signature Schemes) the input and output bitstring of the OWF and the message digest have the same ...
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518 views

Are there any Implementations of Secure Indexes? [closed]

There are several papers about Secure Indexes, for Example "Searchable Symmetric Encryption: Improved Definitions and Efficient Constructions" and "Secure Indexes". ...
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198 views

Full encryption of IDs, partial decryption with customer specific key

I am looking for a "partial" encryption/decryption algorithm. Let's say I am encrypting the following List of IDs (long values) $[1,2,3,4]$ (with a secret key) to an encrypted string $e$, I would ...
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2answers
317 views

Should I bother implementing DH + AES, or leave it to a library like Crypto++

I'm making a C++ back end for an application that'll heavily rely on AES-256 and DH. Should I trust third party libraries, or spend (lots of) time to learn about cryptographic implementation and write ...
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4answers
624 views

Are specially designed fonts sometimes used in cryptography?

As a font designer, I was thinking that it would be very easy to design a special font that could either jumble characters of a language (or of a code) or simply (with the features offered by the OTF ...
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147 views

What does the TLS 1.2 client finished message contain?

I am implementing TLS 1.2 and I'm stuck on the client finished message. My question is: what is the size and structure of a clients finished message in TLS 1.2 when using the ...
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1k views

If you had to implement the BGN Cryptosystem, how would you do it?

If you had to implement BGN, how would you do it? I'm looking for an implementation of the public-key cryptosystem due to Boneh, Goh, and Nissim (aka BGN), or at least some suggestions on ...
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2answers
7k views

How to distribute session keys in public key cryptography?

In public key cryptography we can also use session keys which are symmetric. How do the sender (say a server) provides this session key information to its clients? If the sender (here server) ...
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223 views

What should I be aware of when implementing algorithms myself?

I plan to build my own crypto library. The project will be primarily for me to learn (and if useful for no other purpose, that is fine). In the past I have implemented a few hashes, and AES quite a ...
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2answers
669 views

GCM encryption for 256-bit and 512-bit block ciphers

The Galois/Counter Mode of Operation (GCM) This paper describe using GCM mode with 128-bit and 64-bit block cipher. Can we use this mode for 256-bit and 512-bit block cipher?
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870 views

Additive ElGamal cryptosystem using a finite field

I'm trying to implement a modified version of the ElGamal cryptosystem as specified by Cramer et al. in "A secure and optimally efficient multi-authority election scheme", which possesses additive ...
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214 views

Addition step in MD5 implementation

In MD5, there are four rounds. After every round, why do we need to add the computed $Q$ values to the initial values and then take this value as input to the next round. For example after the first ...
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319 views

Difference between Hardware implemented algorithm and software implemented one?

In the articles about cryptography I see the words Hardware implemented and Software implemented. I'm curious to know what is the difference between them? In the other words, even in the computer ...
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3answers
295 views

Can padding length, and thus plaintext length, be considered public information when using aes-cbc?

Right now I'm using a simple padding system that takes the plaintext, hashes it with SHA512, and appends $x$ bytes of the hash as padding where $x$ is the delta between the plaintext and nearest ...
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1answer
53 views

How can bit slicing be constant time, when Mix Columns is in the cipher

I'm reading about bit-slicing techniques, and one thing about it caught my mind. The strength with bit sliced implementations are (apart from that they are fast) that they are running in constant ...
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88 views

What is the difference between MACTripleDES and TripleDES?

I was asked to encrypt/decrypt a string using MACTripleDES. Is there any difference between MACTripleDES and TripleDES? If, where exactly is the difference between both?
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Pseudocode for constant time modular exponentiation

I'm looking to implement modular exponentiation (for RSA) in constant time, but most of the examples I've found are more mathematical descriptions of the operations. Are there any references with ...
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70 views

What is the recommended number of iterations for Argon2?

I've recompiled my operating system ("LionBSD" based on FreeBSD) to use Argon2i as the default password hashing algorithm in crypt/libcrypt. I'm wondering what the recommended number of iterations ...
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542 views

Blockwise Montgomery multiplication

I have to implement a 256*256 bit Montgomery multiplier for pairing computations. The straightforward approach is to use a bit-serial version, but I would like to utilize the built-in 64*64 bits ...
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968 views

Is this a correctly formatted PGP session key packet?

RFC 4880 may be full of information, but it can be incredibly vague at times, so im looking for someone who actually knows the answer to this. Given this public key: ...
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2k views

What is the 'Version Incompatibility" Problem in TLS 1.1/1.2 and 1.0?

It's unclear to me if there are multiple problems, or a single one, (and just what that problem is) with servers incorrectly negotiating down from a client offering 1.1 or 1.2 to something they ...
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2answers
103 views

Are there simpler FHE methods than Craig Gentry's original paper?

Craig Gentry's 2010 paper on FHE is very cool, and I'm planning on implementing a basic proof of concept FHE. I was wondering though, are there any simpler methods that have been discovered since ...
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189 views

Parallelization of CFB mode encryption and decryption

While reading Evaluation of Some Blockcipher Modes of Operation by Rogaway (someone just linked it somewhere), I noticed two claims about CFB that I'm not sure I understand: Regarding whether CFB ...
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445 views

In ECDSA, how many field operations are used for signature verification?

I am wondering about the computational cost of ECDSA signature verification, in term of multiplications in the base field; and, as an aside, in term of (much cheaper) additions. To make things ...
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2answers
581 views

Verilog simulation & synthesis of Diffie-Hellman key exchange

Is there any freely available verilog implementaion of Diffie-Hellman key exchange? I couldn't find anything using google. So, assuming its not there I started implementing on my own. The code is ...
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305 views

Undecrypt using the OpenSSL EVP API?

I'm writing a client-server encryption scheme for homework, and I've stumbled upon what might be a fatal blow to my current implementation. When using AES-256-CBC on the two sides, it's important ...
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309 views

Best choice of finite field for AES on a 4-bit microcontroller?

As the finite field of $GF(2^8)$ are isomorphic to $GF((2^4)^2)$, $GF((2^2)^4)$ and $GF(((2^2)^2)^2)$, which of the fields is best suited and most efficient for 4-bit MCU and why? Would it be $GF((2^4)...
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58 views

Can the attack in https://eprint.iacr.org/2008/469.pdf be parallelized?

Can this attack be parallelized? It is a $2^{57}$ complexity collision attack on SHA-1 based on disturbance vectors. If it is practical it is easy on a GPU ($\approx1.1$ GPU-days). If it is ...
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1answer
186 views

Implementing AES MixColumns with fewest XOR gates

I'm playing with Contiki (O.S. for constrained devices such as sensors and micro-controllers) and particularly with the AES encryption in software (the one available in Contiki source code). I'm ...
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6k views

How to obtain KCV from the key

Simple question: we have AES 128 encryption and a key. How can we calculate the key check value (KCV)? One example: key is 48C3B4286FF421A4A328E68AD9E542A4 and KCV should be 77DC84. I am trying it ...
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1answer
3k views

Who uses the RSA BSAFE library? [duplicate]

Who uses RSA's BSAFE library? Does anyone know what products use it, or have any statistics on how many end users use something that is built on BSAFE? Background: BSAFE is one of the oldest ...
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237 views

Length of data to hash for PGP

I have finally managed to verify some simple PGP signed message blocks. However, I discovered that for some reason, my implementation limits me to verifying data that is 9-16 bytes long. no less. no ...
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48 views

Ideal way to profile/performance-measure cipher implementations

I have implemented a bit-sliced version of two ciphers (Gibbon-120 and Hanuman-120, both part of the Primates family of ciphers: http://primates.ae/wp-content/uploads/primatesv1.02.pdf ) I now want ...
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8answers
838 views

Does a public key absolutely need to be used to initiate an encrypted session?

I am a software developer working on an application with the .NET platform. This application needs to provide a secure connection and encrypt all data between the client and the server. It is a ...
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4answers
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Where i can find an AES implementation in python? [closed]

Where i can find a "reviewed" version of AES implementation in python. Not an API like PyCrypto whereby you can call AES algorithms in a single line.
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3answers
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How can I avoid calculating with huge numbers when implementing the RSA algorithm

There is 26-letter English alphabet. There is the plain text: TRYAGAINLATER. I need to encrypt it by RSA algorithm with the public key 53. What is the ciphertext? ...
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3answers
676 views

How to avoid a chicken and egg scenario with encrypting passwords?

I am working on application that allows users to upload files containing company data and then share those files with a list of other users that have specific roles within the system. I want to ...
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2answers
446 views

What cipher mode is suitable for independantly decryptable short messages?

I'm building a small VoIP client which transmits encrypted audio data via UDP, and some packet loss is expected, so each packet will need to be decrypted separately even if others in the stream don't ...
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3k views

How to perform file encryption using 128-Bit AES?

I am confused, how can I encrypt a file using 128 Bit Advanced Encryption Standard? Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? Is ...
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2k views

Why do all hash functions use big-endian data?

I've looked at several hash function specifications, and they all emphasize the need for big-endian byte ordering. Is there a reason for this that has to do with security, or is it simply convention?
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417 views

Avoiding overflow when encrypting with RSA

When encrypting with RSA one calculates $ m^e \pmod n $ by doing the following: m^e % n Where $m$ is what we encrypt. Often $e$ is a very big number to make it ...
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141 views

Is the use of AES in LoRaWAN correct?

I'm reading about LoRaWAN (specification). This network protocol has a particular way to encrypt data, detailed in the part 4.3.3.1. Here is a recap of how the encryption work, as I understood it. ...
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1answer
226 views

Encrypt with one cipher and decrypt with a different cipher?

I recently installed an android app called Secret Space Encryptor and think I found a serious flaw in it. Let me explain: This app provides a variety of different ciphers to use and I used Threefish ...