# Questions tagged [encryption]

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.

3,029 questions
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### Euler's totient function and Carmichael's totient function in RSA [duplicate]

I'm a high school student taking IB and I'm doing my EE on Maths, more specifically on the effectiveness of Euler's totient function and Carmichael's totient function in RSA. Am I right in thinking ...
3answers
282 views

### What are some real world examples where one time pad encryption is used or can be used?

I understood that One-Time Pad (OTP) encryption ensures perfect secrecy. However, I couldn't find any real-world examples where the OTP is used. Also, which are some real-world examples where it won'...
1answer
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### Which type of non-basic cipher works better with microcontroller which has no interface and keyboard connected to it? [on hold]

Did a C++ code on Caesar Cipher to do encryption and decryption with my XMC4500 microcontroller but my lecturer said that Caesar Cipher is too simple. He wants me to use a non basic type of cipher and ...
0answers
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### I need help understanding and answering this question about RSA Enc/Dec [on hold]

Let's assume, Alice's public key is ($N = 15,\space e= 3$), private key is ($N=15, \space d=3$). Bob sends message $m = 5$ by encrypting it with Alice's public key. Attacker Eve intercepts that ...
1answer
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### GCM optimisation using $M_0$ and $R$ tables - Calculation of $R$

I'm implementing GCM in C as a way to learn about it. In the paper titled as The Galois/Counter Mode of Operation (GCM) by McGrew and Viega on chapter 4.1, page 11, 12, they talk about the ...
1answer
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### Does encrypting with MGF1/SHA-512/1024-bit seed equal to a 1024-bit key block cipher?

Suppose: Alice uses SHA-512 with MGF1(as in PKCS#1 V2) and a 1024-bit random seed to generate a mask, XORs the mask with a message(M), gets a cipher text (CT), and sends the CT to her old friend Bob....
1answer
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### How can I derive an ed25519 key pair from a secp256k1 key pair? [duplicate]

Alice has a secp256k1 key pair that she used some time ago when she communicated with Bob. Bob can no longer user secp256k1 but he only uses ed25519 instead. Alice and Bob cannot exchange any messages....
2answers
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### Encrypting/Decrypting sensitive information for storage purpose

I want to store account numbers and routing numbers into SQL database, and i was looking for best way to encrypt/decrypt this sensitive information. After researching i found i can use symmetric (like ...
0answers
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### Difference between Sibling Intractable Function Family and Secret Sharing? [on hold]

What is the difference between any Secret Sharing Scheme Link and Sibling Intractable Function Family (SIFF) Link?
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### How to Accelerate Openssl Library using CUDA C [on hold]

How to accelerate openssl library on GPU for performing faster cryptography
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### Is there any identification for common encoding/encryption?

I come across lots of tokens which might be simply encoded and not random, but I don't know any way to identity if they are encoded or random, how to find is there any cheatsheet for the same. For ...
0answers
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### What kind of encryption algorithms are used in avia and space? [on hold]

It is well known that the security of communications in this environment is very important.
1answer
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### Can you derive ed25519 keys from secp256k1?

Alice has a secp256k1 key pair that she used some time ago when she communicated with Bob. Bob can no longer user secp256k1 but he only uses ed25519 instead. Is there a secure algorithm that Bob can ...
0answers
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### How to change the known ciphertext so the known plaintext is changed in AES CBC mode?

I already read a blog about the padding oracle and also some posts about how to change the plaintext but it didn't work out. So I have the encrypted cookie (AES_CBC): ...
1answer
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### ZKP: Asymmetric encryption with confidential message and known hash

I'm searching for a ZKP package that supports asymmetric encryption so I can implement following scenario : Carol encrypts message $m$ with Alice's public key and sends the ciphertext to Alice. Bob ...
0answers
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### Elgamal Encryption Scheme [on hold]

If we have a message with size 72-byte and the message is encrypted using Elgamal Encryption Scheme: What is the size of the ciphertext? How much time does it take to encrypt the message (ms)?
0answers
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### Three challenges of varying difficulty [closed]

I have been solving online coding puzzles for about a month now, which all started with one of my friends finding a flyer in the food court of our university. Many speculate that it is an IT firm in ...
2answers
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### Extract one unique SBox from Canonical Representative

In paper https://eprint.iacr.org/2011/218.pdf, the author has examined 16! different 4 bit SBoxes and at the end of investigation, introduced an optimal class which named "Golden SBoxes". How can I ...
1answer
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### Difference between RC2, RC4, RC5 and RC6

Can anyone point out the core differences between RC variations?
0answers
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### How can i solve following question? [closed]

Any hint on how I could find plain text from following cipher text? SR PUUG MBZ KHMS YUYWWP MIXF TOSNDVZ Also the message was supposed to encrypted by using Caesar cipher substitution then by using ...
0answers
33 views

### Any hint on how can I find plain text from following cipher text? [closed]

Any hint on how I could find plain text from following cipher text? SR PUUG MBZ KHMS YUYWWP MIXF TOSNDVZ Also the message was supposed to encrypted by using Caesar cipher substitution then by using ...
3answers
1k views

### Does adding complexity mean a more secure cipher?

I have a cryptography workshop question I'm having trouble with as follows; Person A creates a cipher $E_k(m)$ which produces a ciphertext from message "m" using key "k". The function inside E is ...
1answer
22 views

### Difference between one-way encryption, Transparent data encryption (TDE) and data encryption

What is the main difference between one-way encryption, Transparent data encryption (TDE) and data encryption? If one needs to store passwords or credit card details in the DB, which one is best to ...
0answers
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### How to decrypt sensitive information with a token and a password [migrated]

In a web app, it's common practice to encrypt sensitive information against a user's password. In this scenario, what's how would you access/encrypt/decrypt that information using token based ...
1answer
4k views

### Is encryption time greater than decryption time?

Is encryption time always greater than decryption time for all encryption techniques (AES / DES / RSA / DSA), or is there a mistake somewhere in my implementation?
2answers
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### Is there a crypto system doing sqrt during encryption?

This is a theoretical question to solve an argument with a friend.. Is there a working cryptographic system that do square root operations during the encryption process? "Working" means that it is ...
0answers
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### Is it possible to encrypt a user’s email in a zero-knowledge way and still send them emails?

This is kind of hypothetical, but let’s say I have a web app and I want to store a user’s email for sending notifications to. Is there any zero-knowledge way to hide their email from ourselves and ...
0answers
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### RSA encryption extremely large public exponent

I'm trying to do learn a bit about RSA by doing CTF's and now I am doing one problem probably more than 7 hours so I would really appreciate a hint here from an expert. I have an encrypted message $c$...
1answer
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### Methods of Learning Cryptography [closed]

We're currently approaching the end of our semester, but I've found that our homework is starting to consist more of encrypting and decrypting using different types of algorithms instead of learning ...
1answer
488 views

### 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 (expired) harder to implement constant time more expensive in hardware ...
1answer
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### Question on using endomorphism on secp256k1 and negative results

I have read section 3.5 (algorithm 3.7) in "Guide to Elliptic Curve Cryptography", and have been trying to implement endomorphism on secpt256k1 to speed up calculating $kP$ by changing it into 2 point ...
1answer
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### Why is encryption slower than decryption in elliptic curve cryptography (ECC)?

While performing encryption using public key and decryption using the private key, I am always finding that encryption takes more time than decryption in elliptic curve cryptography (ECC). It's the ...
2answers
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### what is the state of the art algorithm to encrypt credit card data

We have a business requirement to keep credit card data. What is today's (Nov 2013) state of the art algorithm to encrypt credit card data that will be saved on disk? Additionally, I'd appreciate ...
1answer
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### Can not use big prime number for pair of key of RSA Algorithm [closed]

I'm new to cryptography. I have a binary image with 64x64 pixel in size. I perform an encryption to the image using RSA Algorithm. I wanna ask something bothering me, why can I not use big prime ...
2answers
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### How to produce a binary output sequence using LFSRs but with increased linear complexity?

How to produce a binary output sequence using LFSRs but with increased linear complexity? I have tried searching but i got confused on equation details. So can anyone help me with rather simple ...
0answers
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### Unix salt for passwords - length doesn't matter in offline dictionary attack?

Lets say an attacker has gained permanent access to the password file and mounts an offline dictionary attack. The passwords are stored as hash values in the file together with a salt values, ...
2answers
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### How to know the difference between two ciphertexts without key stream in stream ciphers [duplicate]

If I have two cipher texts lets say $C_1$ and $C_2$ of the same length encrypted through stream cipher technique using the same keystream. Let's say they are: C_1: \texttt{96 C6 A1 08 E7 F2 33 3B ...
0answers
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### What is the most secure way to encrypt certain properties in logs

I would like to encrypt certain data before logging it. Currently, I use a private key and a static IV. Looking at generating a suitable IV I am concerned about the overhead in generating CSPRNG ...
0answers
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### XOR operation to uncover plain-text out of given cipher-texts [duplicate]

I have a set of 11 hex coded strings that have been encrypted using XOR operation each with the same stream cipher key. How do I decrypt the 11th hex-coded string to arrive at the plain-text without ...
1answer
3k views

### AES: Why is it a good practice to use only the first 16 bytes of a hash for encryption?

I'd like to encrypt Text with AES/CTR and a password defined by the user in java. I already checked the internet (and stackoverflow) for answers. The most used version is to hash the user password ...
0answers
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### Strongswan KDF Test

How can a KDF implementation for IKEv2 application, specifically in strongswan implementation case can be verified for conformance with NIST SP800-135, please? SP800-135 KDF recommendation further ...
4answers
530 views

### Can “collisions” occur with encryption algorithms?

For a given Key $K$ and two messages $m_1, m_2$ is it possible for an encryption algorithm (say AES-256) to produce this: $AES(K, m_1)$ = $AES(K, m_2)$? I understand that the output has to be unique (...
3answers
2k views

### When is a cipher considered broken?

We've all read how some people claim AES is broken because there was supposedly a way to get the plain text from a cipher text faster than brute-force. But is this the definition? Is a cipher broken ...
2answers
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### Is it possible to use X.509 for a symmetric-key algorithm?

I read on wikipedia what is X.509: In cryptography, X.509 is a standard defining the format of public key certificates. X.509 certificates are used in many Internet protocols, including TLS/SSL, ...
3answers
2k views

### Can one claim that AES is a perfect cipher?

I'm taking a crypto class this semester and after learning the definition of a perfect cipher. I started wondering how this definition applies to AES. Obviously AES isn't a perfect cipher, since the ...
1answer
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### Encryption: am I doing it right?

I'm trying to get a per-user encryption key scheme off the ground and need some validation from wiser crypto pros. Consider the following procedure: User provides registration information to include ...
1answer
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### How do i approach file encryption using encrypt-then-mac? [duplicate]

I'm programming a cryptographic application that encrypts files, locked with the password the user supplies. It's not intended to be used in production. It's a project for me to learn more about ...
3answers
8k views

### Encryption/ciphers/codes in Chinese

I am quite curious as to how you can perform simple encryption for the Chinese language. Saw a similar question related to encryption/Chinese here: About cryptography in a character language, ...
2answers
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### Is there any encryption algorithm that, with small change in input will produce big change in the encrypted output?

As stated in the title, I'm looking for an encryption algorithm with the characteristics that, when inputs are slightly different, the encrypted output will be VERY much different, to the point that ...
5answers
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### Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...