Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Do data-dependent rotations have any advantage over fixed rotations?

There are many ARX ciphers, however most use fixed rotations. I know data-dependent compared to fixed rotations are: patented harder to implement constant time more expensive in hardware harder to ...
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plaintext distribution ,perfect secrecy cryptosystem

I have been trying to solve the next problem: let pi be a perfect secrecy cryptosystem with specific plaintext probability distribution. How to prove pi will have perfect secrecy for all other ...
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How many of primitive point on the elliptic curve?

In elliptic curves for cryptography, I know $nG=O$, where $G$ is a base point represented by $G=(x_g,y_g)\ on\ E(F_P)$, where $n$ is Order of point $G$. For example, $P(0,6)$ is a primitive point on ...
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192 views

Key derivation for AES-Encryption key and HMAC

Okay so I have two options for how I would derive two keys for AES encryption and HMAC they are as follows: Run BCrypt on a users passphrase and then use the bouncy castle implementation of HKDF in ...
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115 views

What is primary security in ECC?

I read the following paragraph in a book about Elliptic Curve Cryptography, but didn't understand it: The primary security in ECC is the parameter $n$; where $n$ is Order of point $G$, that is $n$ ...
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107 views

Best practices (if any) to add metadata to encrypted files

I am encrypting files using AES/CBC/PKCSPadding, with 256 bits long keys. So far the first 16 bytes of each encrypted file are the IV. I would like to store some more information regarding the ...
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228 views

RSA-KEM construction

"Create a random key for CCPA2 scheme, encrypt m, send it along with a PK encryption of the symmetric key. " Say in the process, the KDF is HMAC, then: get a random key (128-bit) C1 = encrypt ...
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3answers
107 views

How a file is encrypted?

I thought encryption algorithms(like AES) are used to encrypt texts,so how a file or folder(containing pictures,videos,...) is encrypted?What is encrypted exactly?
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5answers
540 views

Can hashing become encrypting?

hashing some data and encrypting data share some similar attributes. Surely this is why "Difference between encrypting something and hashing something" has been asked. The point of this question is ...
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150 views

Using bcrypt derived keys for encryption?

Sorry for this ignorant question but I am currently weighing up the advantages and disadvantages of BCrypt over PBKDF2 and from what I have read BCrypt is considered more secure but from what I have ...
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51 views

Why has SSL v3 not yet been upgraded to a higher version with stronger principles, what are the dependencies and issues to do so?

SSLv3 is almost 18 years old; why has it not been updated to a more advanced version with stronger rules and structure. What have been the issues and dependencies in doing so till now???
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2answers
284 views

Can RSA signing be implemented on top of RSA encryption/decryption?

I need to use RSA-SHA256 signing. Unfortunately not all Microsoft CryptoAPI providers support that. It's possible that I might get a handle to a CryptoAPI provider that can just encrypt/decrypt with ...
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Opinion on my idea for storing credit cards securely

I've been thinking of ways to store credit cards securely, I thought of this: Take the users credit card info Put the card info in a standard format "Full Name/Card Num/Security Num/Expiry ...
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65 views

How can I calculate the size of an encryption key?

I have encryption algorithm that has two variables are used as encryption key. How can I calculate the size of the encryption key. I will show an example of what the variables can be: ...
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0answers
29 views

Do OpenPGP SmartCards have the same or better security than an air-gapped machine?

Are OpenPGP SmartCards, such as the OpenPGP SmartCard V2, suitable enough to have secure communications? Meaning, if I connect my smart card to my Mac which is connected to the internet and always ...
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1answer
120 views

Determining message given cipher-text and public key [duplicate]

Consider the following scenario: Suppose A and B have set up their RSA public keys, namely $(e_a, n)$ and $(e_b, n)$, where the n-value is the same. Also, it happens that the $\gcd (e_a, e_b) ...
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127 views

Why is there an extra block when encrypting? [on hold]

I am passing input data 20 bytes long and java AES-CBC returns 48 bytes instead of 32 which is what I think it should output because of padding. My key is 16 bytes long. ...
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2answers
439 views

Is RSA encryption of a cryptographic hash with a private key the same as signature generation?

It is often said that RSA encryption with a private key is the same as signing (signature generation). Will RSA encryption with a private key over a cryptographic hash give the same result as ...
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Crypto-Compression Algorithms?

I was wondering, whether there exist such algorithms/enciphering procedures which both compress and encrypt the input data. That means, for starters, the output will be both smaller in size and ...
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192 views

Brute Force AES Calculations

I have an encryption service in which the user decides the length and the type of key, so I would like to build a tool that educates the user on the brute force times for the key they created if using ...
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187 views

RC4 encryption/ decryption with hashing

I am working on RC4 encryption/ decryption algorithm based on the following: A wants to send M to B, for that A did: H = Hash (K||M) C = Ek (M||H) A sent ...
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80 views

Multi-round Transposition/Playfair as a secure hand cipher in the computer age

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
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47 views

How good is middle cube method with jumbled digits?

I had to make my own prng for a stream cipher for an inter school science project (I am mentioning that a lot). So I thought of cubing the seed instead of squaring it (like in the middle square ...
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symmetric encryption A5/1 and A5/2 algorithms

where does the key (Kc) used to generate the keystream comes from and also where does the 22bits counter comes from
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98 views

Show that the equal difference property exits for a modified DES encryption system

My cryptology professor gave us this problem on a past homework assignment and I only managed to get one of the 3 parts correct. Needless to say, I want to know how to do the other two parts as well. ...
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72 views

How can a good encryptor be made?

I am making an encryptor software for a stream cipher with my own PRNG as a project for an inter school science competition. How can I make one so that after it generates the pseudo random nos. it can ...
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Can you explain “weak keys” for DES?

A weak key for DES is a key $K$ such that $DES_{k_1}(DES_{k_2}(x))=x$ for all $x$. I don't get why are the 4 keys $k_1||k_2$: $1^{112}$, $0^{112}$, $0^{56}||1^{56}$, $1^{56}||0^{56}$ considered as ...
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Cryptographic system with double keys with reversible order

While reading Shamir, Rivest and Adleman's paper on "Mental Poker", I've met a mention of system such that $E_a(E_b(x)) = E_b(E_a(x))$, without however disclosing details on it, with $E_a(x)$ being ...
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1answer
178 views

How can a good pseudo-random number generator be made?

I am trying to make a pseudo-random number generator so that I can use it in a synchronous stream cipher for encrypting plain text. I want it to generate numbers which are as random as possible. What ...
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281 views

Simplest code for 64-bit block RSA-like encryption/decryption and key generation

Looking for the simplest code in C. Need a set of functions that will first generate a public/private 64-bit key pair, and then the function to code/decode a given 64-bit block, no built-in checksum ...
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79 views

Type of cipher used where ciphertext has no discernible pattern, spaces. Type?

What type of cipher could give ciphertext where for example random ASCII chars between say F-z (symbols and numerals inclusive), but with only a few spaces? Frequency of chars shows some similarities ...
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78 views

Public key encryption without ciphertext expansion

Say I have a database column that is defined as VARCHAR(255) that stores names. I can assume that names can be up to 255 chars. I need a public key encryption so that I can replace names with their ...
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486 views

Why does openssl use SHA1 in ECC when I use secp384r1 curve

I need a small clarification that why openssl using SHA1 in ECC when I am using secp384r1 curve, but in rfc they are saying we should use SHA2. Thing here is am using nanoECC in my DTLS, nanoECC ...
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Why is the IV passed in the clear when it can be easily encrypted?

The initialization vector (IV) is exclusive or'd against the plain text before encryption for the first block sent in order to prevent an attacker from learning that duplicate message blocks are being ...
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Are there any many to one encryption frameworks available?

I am reasonably new to the cryptography. For my use-case I need a method where in I would need a receiver to accept encrypted messages from a range of senders (each having their own, say, public key). ...
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65 views

Client-server communication

The base scenario goes as follows: A program stores some user's confidential data encrypted on their disk. The user is most probably clueless and the disk might get stolen, but these are the classical ...
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181 views

How to encrypt letters less than block n using Hill Cipher

I am learning about Hill Cipher and know that it is a block cipher where each block of n letters (considered as an $n$-component vector) is multiplied by an invertible $n \times n$ matrix, again ...
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244 views

Frequency analysis of Vigenere Cipher

For Vigenere cipher, I understand Find period first (say we have p = 6) Find highest frequency of letter in each group (from 1 to 6) and assume it is "e" in plaintext What if we have more than ...
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96 views

A one way Function provably reversible at N applications with the same seed?

I'm looking for a function that is generally one way from some secret $F(s, A) \rightarrow Y$, where $A$ is known, $Y$ is produced (also known), and $s$ is kept secret. But whose repeated application ...
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135 views

Number of keys for a monoalphabetic cipher

My teacher stated that… The number of possible keys (E) in a monoalphabetic cipher is $26$! My thinking: Every letter in the alphabet can be $25$ different letters hence it the number of ...
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Are password salts equivalent to keystream?

I was reading up on keystream when I came upon the definition of it: A keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted ...
6
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500 views

What do you call one time pad where pseudo-random numbers are used?

What is the encryption method called when pseudo-random numbers are used instead of true random numbers?
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143 views

Operation which needs much computing power to be created, but just a little to be solved?

Does somebody know a cryptographic/mathematic operation, that needs much computing power to be "encrypted"/"created" but doesn't need much power to be "decrypted"/"solved"?
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551 views

Format Preserving Encryption for 32 or 64 bit plaintext values

I am looking for a Format Preserving Encryption implementation to apply to either a 32-bit or a 64-bit integer. It looks like AES/FFX mode is just what I need in terms of established security ...
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1answer
83 views

Convert message to polynomial NTRU

How to make a message into a polynomial? I saw many answers to this question and yes, i know that here are some questions. But i did not get it. I think that i am making some mistakes. I took a word ...
4
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1answer
116 views

Generic group model: use of polynomials in the proof of the master theorem

I've been looking at the paper of Boneh, Boyen, Goh Hierarchical Identity Based Encryption with Constant Size Ciphertext which contains a general theorem (Theorem A.2) about the advantage of an ...
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84 views

Prepending random data to encrypted file

If random data is prepended to a file encrypted with GNUPG's symmetric encryption, how may an attacker find out if the input file is deliberately corrupted or the passphrase is wrong? If it is not ...
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321 views

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 ...
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ZIP 2.0 encryption bruteforce attack

I have an old sourcecode backup from my DOS days stored in a ZIP 2.0 encrypted archive, but I lost the password. The password was written on a paper slip, but I remember that it consisted of 30+ ...
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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 ...