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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Is this an acceptable implementation of ARC4 encryption for my system?

I am building an open source hardware system that will be used to control things over the internet. The system consists of a Base Station and Modules which use wireless communication at 2.4GHz to ...
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155 views

Can you help me with this DES variant analysis?

I'm struggling with some DES variant that I got as an exercise (exercise taken from Katz-Lindell Ex5.14). The variant is as follows: The left half of the master key is used to derive all the ...
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Help me about Advanced Encryption Standard (AES)

Suppose $E_k$$(a, b, c)$ is encryption of values $a, b$ and $c$ with key $k$ through encryption algorithm AES (AES-128) and each $a, b$ and $c$ are 300 bits integer values. Also Suppose this ...
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370 views

Computing p and q from private key

We are given n (public modulus) where n=pq and e (encryption exponent). Then I was able to crack the private key d, using Wieners attack. So now, I have (n,e,d). My question is, is there a way to ...
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95 views

What is the security risk if an encryption key is not random?

Ok, I just jumped into crypto and now struggling with some points… I read lots of resources, most of them mention how important the strength of the encryption key is. However, I could not find much ...
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144 views

Repeated Encryption using same/different Encryption systems [duplicate]

I would like to know if there are any security risks/gains from encrypting twice, i.e. $$\text{plaintext}\xrightarrow{encrypt}\text{intermediate text}\xrightarrow{encrypt}\text{ciphertext}.$$ I would ...
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312 views

Does ElGamal Encryption create a different key for each block sent?

I ask about ElGamal algorithm. Is ElGamal algorithm used new key for each encryption process. in other word it should we use new key for each chunk? For example, if we have message that has four block ...
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617 views

Using Whirlpool hashing function to encrypt data

I've read that the Whirlpool hash function can produce footprints that could be used as a pseudorandom generator. Is it "OK" to use it to encrypt some data using something like the following? ...
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141 views

Multiple parties must encrypt and get the same result

Hopefully this question is not too simple - I did some research but with encryption I really don't want to make a mistake. Our scenario is that multiple groups need to encrypt a number and arrive at ...
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116 views

Security of CFB on a public channel

Given a server that broadcasts all received data to all connected peers (except the sender), two participants can have an encrypted conversation using a self-synchronizing method like CFB and some ...
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2answers
143 views

How to compare two datasets „anonymously”?

Ok, I hope this question makes some sense because I am not so sure how to word it any differently… Imagine the following situation: There are 10 defined colors (blue, orange, yellow etc.) There are ...
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631 views

Security of Deterministic Encryption Scheme

A deterministic encryption scheme is a cryptosystem which always produces the same ciphertext for a given plaintext and key, even over separate executions of the encryption algorithm. Although we ...
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238 views

Can you help me understand how RC4-52 is done using pen-and-paper?

I've played a lot with VIC and enjoy its complexity and effectiveness as a field cipher. However, RC4 has caught my attention lately and I've read there is a RC4-52 variant that can be done by hand. ...
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219 views

Zero-Knowledge Challenge-Responce Protocol

Good day to everyone. I am trying to implement an e voting system (just for reference -it is not important though-it is described at the Internet Voting Protocol Based on Improved Implicit Security ...
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2answers
170 views

RSA keys finding when messages are known

I have this situation, where, in a game, people send messages to each other (game moves etc...) These messages need to be encrypted, and should only be readable by the destination person. I am using ...
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2k views

Calculating the inverse modularity of the determinant for Hill cipher

I'm trying to decrypt a message encrypted with Hill Cipher, but I don't understand how to find the determinant so it solves the equation $det * 1/det = 1 mod 26$. The determinant for my key matrix is ...
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304 views

Generating a cryptographically secure, many-time use, symmetric encryption key

I need to generate a 256 bit encryption key described by the adjectives in the title. Currently I intend to create the key using this RNG. Is this a secure manner of creating the key, given that it ...
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436 views

Using “Additional Authenticated Data” as a secondary key

In implementing a cipher in GCM or CCM mode, you are provided the option to add "Additional Authenticated Data" (AAD). This AAD is required for decrypting the cipher text, and seems to be used when ...
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238 views

AESManaged Trade Compliance Issue in United States

I am currently using AESManaged encryption for my silverlight application. Does AESManaged encryption have a severe trade compliance issue in Bureau of Industry and Security in terms of shipping the ...
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66 views

Encrypting decryption key

What's that property called when a scheme is secure even if you encrypt the decryption key? Some schemes have problems when your plaintext is the decryption key (or just the key if symmetric).
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Is AES-GCM length extension attack possible using authenticated decryption?

I am looking to encrypt a piece of data using AES-GCM with a full 16-byte GCM Tag and send it over the network using UDP. Is it safe to assume using the AEAD nature of AES-GCM that performing ...
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68 views

Use of ElGamal encryption for signature generation

If RSA (textbook RSA that is) generates a digital signature by using the sender's private key, couldn't any cryptosystem (the only two that come to mind are RSA and ElGamal) capable of asymmetric ...
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70 views

Verification of signed message with encryption

I have a question about the message that is being encrypted and signed. Say, two users called Tom and Mary, both have a pair of private key and public key. Tom sends a message through a system that ...
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58 views

Encrypted files in an encrypted partition or folder

Recently I started wondering about multiple encryption and found pages upon pages of posts and debates about the security of cascades. Now, don’t worry – I'm not looking for someone to discuss a ...
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108 views

Secure way to store fixed size string of digits

I need to store a string of digits (0-9) of a fixed size in my database securely. I've already performed a rainbow table attack on a plain hash, and it broke it in a matter of seconds. One option I ...
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How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?

Edit: I know this isn't really a one time pad (as pointed out), though I don't really know what to call it aside from just a pad, I guess. I have been reading around (mostly various stackexchange ...
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98 views

How to find which padding method is used in Block cipher(AES) encyption?

I have a cipher text which is encrypted using AES128 Algorithm. I want to know the following things to decrypt the cipher. IV (Initialization Vector) Padding Method Encryption Key How do I find ...
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297 views

How can I calculate the Rijndael SBox?

I would like to implement the Rijndael subBytes() operation using calculation instead of tables, because I like to play with this on different wordsizes, as an ...
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1k views

The modulus of RSA public key

I am studying the RSA cryptosystem. The public key consists of $(n, e)$, the modulus (product of two large primes), and the encryption exponent. I want to separate the modulus $n$ and exponent $e$. A ...
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105 views

Comparing two values without revealing them

Suppose Alice wants to prove to Bob that t1 is less than t2. t1 and ...
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303 views

Encryption of log files

I'd like to encrypt the contents of a log file that my application writes. The log system has the following characteristics: The file format is binary. Log files are left open while the application ...
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148 views

Pailler and Gentry - homomorphic encryption

Paillier cryptosystem is a probabilistic asymmetric algorithm for public key cryptography. Doesn't homomorphic encryption schemes have regular effects on the plaintext, and does that mean Pailliers ...
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129 views

How do P2P clients like uTorrent maintain authenticity of files?

I am very new to concepts of cryptography so bear with me and feel free to fill in any information that may seem obvious but something you think someone may not know. At first I was under impression ...
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Is HMAC necessary if the AES ciphertext of a message includes the CRC of the message?

I've seen that encrypting an image with AES-CBC then calculating the HMAC-MD5 value for authentication is a somewhat common and sound way to secure data. Alternatively, can I just calculate the CRC of ...
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107 views

With Encrypt-then-MAC, and flexible protocols, do I need to authenticate the authentication?

Sorry, the question is not easy to state (or wasn't for me, anyhow). So I'm writing a very flexible format for security. It allows for full choice of cipher, key size, and so on, along with key ...
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151 views

Good Encryption Exponent

I have placed a bet that I can create a public key such that my adversary will not be able to crack (decrypt) it for at least one week. For my primes $p$ and $q$, I chose very large numbers that are ...
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Storing Credentials for a Third Party

(Originally posted to SOF, but I got no answers) I am designing a small application for use inside my company. My application needs to connect to a third party website on behalf of my application ...
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How does DES decryption work? Is it the same as encryption or the reverse? [duplicate]

If DES decryption is the same as encryption done in reverse order, then how can the reversed S-Box convert 4 bits into 6 bits?
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Encrypt user email but be able to find user by email

Sorry for my dumb question, but it's better to ask dumb question than to do dumb things silently. I want to encrypt user email in my DB so that if someone stole the DB (and not the key) - he won't be ...
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How can mega store my login details and still be secure?

I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works: Upon first signing up for an account you make a ...
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Secure communication between multiple peers on a public channel

I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel. With two peers it is easy - they exchange their encryption keys and decrypt the ...
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89 views

Individual bits of Textbook RSA

This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem. Does RSA hide all ...
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958 views

Difference in one time key and one time pad and many time key

These terms are confusing me. One time pad is when you use one key for one message. That is what One time key is. Secondly, what is the connection of many time key, can i use one time pad many ...
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2k views

In which order are the round keys used during AES decryption?

In the Add Round Key step in AES decryption, which part of the expanded key will I XOR first to the result of the SubBytes step? Is it the 10th round key? For example, is this the right order? ...
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How can I store a combination of multiple pass phrases?

Let's assume we have 2 phrases, one is the real password from a user, and the other is generated from the real password and almost impossible to guess. You would need both to authenticate a user. What ...
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738 views

Where can I find Secp256k1 ECDSA test vectors?

I`m currently implementing an ECDSA library based on curves like secp256k1. I would like to test it using some test vectors, like ...
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26 views

Is it possible: Derived key based on variable number of private keys?

I have a MySQL database that I want to encrypt with AES_ENCRYPT() and have to provide access to a variable and possibly changing number of users. Is it possible to derive an encryption key based on a ...
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49 views

Deduplication: Encrypting the SHA-256 hash of a file chunk

I'm designing a data storage system that should be both able to deduplicate data that share the same encryption key, and be reasonably secure. I know that this kind of encryption quality can be ...
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53 views

Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption?

Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption ? I know that the one-time-pad doesn't have perfect secrecy and doesn't provide ...
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To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure

We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...