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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Two different keys decrypting same content

is there some generally available algorithm which will encrypt a short string and generate two unique keys so that any of the two can be used to decrypt the message again? It doesn't has to be "super ...
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Exchanging encrypted messages, and decrypting without a public key?

I know very little about encryption, but I was hoping someone could shed light on this cipher text exchange scheme I worked out in my head this morning: Bob wants to send Alice a message but doesn't ...
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68 views

What algorithm to use to rotate values in a predefined manner and be able to decrypt them back to the original?

What is the best practice to accomplish this? For example, let's have an initial value abc123456 and a seed secret_hash. I want ...
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Is it safe to use cipher block sizing instead of padding?

I'm using this kind of technique instead of padding of cipher buffer (here goes pseudo-code): ...
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78 views

Encrypt the network adapter mac address so i can get 20 or 25 cipher text length

How do I encrypt a 12 character network adapter mac address so i can get in result with a 20 to 25 cipher text length?
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1answer
151 views

What is the best current way to cryptographically secure databases?

I'm currently working on a proposal for some secure complete system and one of the things currently lacking is the database security. However I don't want to roll my own crypto there and thereby need ...
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264 views

Construct IND-CPA secure encryption scheme by combining two given schemes

I have two encryption schemes $\Pi_0, \Pi_1$, at least one of them is IND-CPA secure but I don't know which one. The task is to construct a scheme $\Pi$ that is guaranteed to be CPA secure and to ...
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100 views

ElGamal in a different group

Can Elgamal be secure in $\bmod {n^2}$? Meaning instead of using a prime order group to use a group where DCR assumption holds?
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132 views

Guessing the IV for CBC

If I have the key, the ciphertext under AES-CBC and the plaintext, then how can I guess the initialisation vector?
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1answer
193 views

Why multiple homomorphic operations on a ciphertext leaks no information about the plaintext?

Scenario: Assume I encrypt message $m$ using Paillier encryption, so I would get $c=E(m)$. I give the identical $c$ to two different parties, parties $D$ and $E$. Party $D$ computes: $c_{D}= E(m)^{...
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1answer
106 views

What are the relative merits of padding algorithms pkcs7, iso7816, and x923?

I am assuming none of these padding algorithms are "the best"... But what are the advantages and disadvantages of using them? PKCS7 is certainly the most commonly used one, but I am interested in ...
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1answer
91 views

Can I store the initialisation vector (IV) in the filename?

I'm encrypting a file and I'm using an initialisation vector. Given that the IV doesn't need to be a secret, is it secure if I add it to the encrypted file's name?
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2answers
95 views

What is the purpose of Pseudorandom Function Families (PRFs)?

I'm currently in a course in Cryptography, and was wondering why pseudorandom function families exist at all. If there existed one pseudorandom function f(x), based on its definition, could that not ...
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80 views

How can I study the math behind cryptography? [closed]

I am a junior in high school and I am currently studying algebra 2. Where can I go to learn about the mathematics behind cryptography? I have a very basic knowledge of cryptography, but I am really ...
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1answer
223 views

How is the AddRoundKey operation performed in AES-256?

Can anyone explain to me (or send a link to somewhere) how round keys are added in AES-256? I understand that the round keys is added to the state matrix for each round and how XOR works. But since ...
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2answers
177 views

Given a pseudorandom function F, is $(F_k(r) \; | \; F_k(r + 1))$ also a PRF?

Given: F is a pseudorandom function, G is a pseudorandom generator with $l(n) = n+1$. The following schemes should be classified as being insecure, IND-COA secure, IND-CPA secure. To encrypt $m \in \...
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313 views

Lightweight Asymmetric encryption algorithm

I'm an embedded systems researcher, and new in the crypto field. Actually, I need to know if there are any lightweight asymmetric encryption algorithm especially considering the time needed for key ...
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0answers
16 views

Lightweight Asymmetric encryption algorithm [duplicate]

I'm an embedded systems researcher, and new in crypto field. Actually, I need to know if there are any lightweight asymmetric encryption algorithm especially from time needed for key generation. I ...
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1answer
87 views

Is my pin algorithm secure?

I'm a hobby programmer and very new to this field. I opened a bank account recently and got two pins. One for the girocard and the other for a creditcard. And I needed two more pins for the online ...
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23 views

802.1X Radius WLAN protected by certificate 1024-bit key

I want to ask you a question. I have WPA-2 (enterprise) network. Also called as 802.1x. I use the Linux Zeroshell distribution, which is optimized for these services. Linux Zeroshell is provides a ...
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1answer
65 views

Which algorithm would be ideal for ephermal key generation followed by DH key exchange?

Bob and Alice, both generate a temporary public key pair each using X algorithm on their individual PC. After being authenticated by a third party, they use the DHE to come to get a common symmetric ...
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34 views

What do you mean by Ciphertext indistinguishability [duplicate]

Wiki definition : A cryptosystem is considered secure in terms of indistinguishability if no adversary, given an encryption of a message randomly chosen from a two-element message space ...
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2answers
634 views

Why is hybrid encryption more effective than other encryption scheme?

Currently I am learning about Hybrid Encryption but I was not able to find any good study material. Below is my understanding: One of the reason why we use ...
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How does darkmail (DIME) work to hide email metadata?

While Email encryption can protect the content of an email, the metadata are still readable and can be used to gather important information about the sender and the receiver. There were several news ...
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How is the ciphertext labeled with a set of attributes in Key-Policy Attribute-based Encryption (KP-ABE)

My question is about Key-Policy ABE (KP-ABE). What does it mean when a "Ciphertext is Labeled with set of attribute"? How is it labeled?
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Message exchange with textbook RSA

I am working on this exercise but can't work out the answer to the question b. I have solved the question (a) by decrypting the ciphertext $C = 2$ using the formula: $$ M = C^d \bmod n = 2^{17} \bmod ...
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Are parts of a pseudorandom string also a pseudorandom string?

I am working on an exercise that encrypts a message using only the first $n$ bits of a pseudorandom generator's output $G(k)$, i.e. $F_k(m) := G(k)_{0...n−1} \oplus m$. $k$ is chosen uniformly at ...
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160 views

Limit the length of AES encoded output to certain value

First let me be clear upfront that am not Crypto expert. I'm having a problem where I will have to use NFC card. Now given the limitation of NFC cards memory sizes, I will need to constraint my system ...
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1answer
101 views

How secure is Shamir's Secret Sharing for password sharing when attacker has t-1 shares?

I am designing protocol to share a random generated n long password between k parties using Shamir's Secret Sharing. I know that share alone does not reveal much information about the original ...
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49 views

How to store keypair generated by RSA in a textfile?

I'm trying to write an encryption decryption program using Openssl-RSA. There are only two operations. User stores the data and retrieves it whenever he needs. To decrypt something, we need the ...
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218 views

Different tools return different ciphertext value for equal input

I have a Luna G5 Safenet HSM and I want to encrypt a text file containing testtest with 3DES-ECB algorithm. So in the first step ...
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1answer
274 views

RSA enc/decryption with multiple prime modulus using CRT

Every information I found on internet about RSA-CRT encryption/decryption uses only two primes. I'm interested in my project in doing that using multiple (up to 8) primes. The general idea is to ...
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95 views

Usefulness of Damgård–Jurik

I am trying to understand what are the benefits of using Damgård–Jurik over Paillier. I understand that expansion factor decreases as s increases. But isn't it the ...
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2 Part Encryption

Can anyone tell me if an encryption / decryption scheme like the following exists? Encrypted1 = SomeCryptoFunction(Data, Key1) ...
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How is the One Time Pad (OTP) perfectly secure?

The Wikipedia entry on One Time Pads (OTPs) states that if this cipher is used properly; ie, the keys are truly random and each "part" of the key is independent of every other "part", it's uncrackable,...
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What is cryptographic agility?

I keep seeing the term "Cryptographic Agility" referenced. What does it mean? For instance: https://msdn.microsoft.com/en-us/library/windows/desktop/bb204775(v=vs.85).aspx One of the key value ...
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311 views

If you encrypt an image (AES), is it still an image and can you view it?

Can you encrypt an image (with AES) such that you can open it as a png/jpeg?
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1answer
241 views

Sorting over encrypted data with different symmetric keys

I'm working on a security project. I need to perform a sorting on the lists of encrypted integers and strings. The encryption used is symmetric. The clients send the encrypted data in a list to the ...
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1answer
116 views

How to calculate mapping in bilinear

I am trying to read a paper in cryptography. In key generation phase, paper give a definition for bilinear like G and Gt be two cyclic groups of prime order p $e: G * G \to G_t$. be a map with the ...
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80 views

RSA Optimal Asymmetric Encryption Padding Beginner

I'm new to the OAEP scheme. I learn it from the Wikipedia page. Link The page does not explain a proper setup for of the system. So I'm not sure if the output of the padding scheme which contains ...
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the decryptNode function for leaf nodes in CP-ABE

can someone please explain to me why decryptNode gives as result e(g,g)^rq(0) for leaf nodes, i don't understand how they went from the sconde step to the third (...
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136 views

Cryptography of numbers

Is there any algorithm capable of encrypt securely (symmetric) N numeric digits in a numeric message of M digits (N < M)? I am especially interested in a specific case in which N = 10 and M = N + 3....
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1answer
100 views

Comparing messages given only the ciphertext

Under RSA protocol I was wondering how a message sent could be verified under the following scenario Alice has a private (encryption key) and public key (decryption key) If Bob sends Alice cipher-...
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59 views

Finding collisions for the DES F-function

It's known that for a given subkey, the F-function of the DES is not injective (see Is the DES F-function injective for a given subkey?). I am interested in efficiently finding collisions for this ...
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Why does GPG ciphertext length differ with fixed plaintext length?

Thank you for your reply. Based on your inputs. I was investigated further, find details below Step 1) Input string for encryption is UUID format Input data = c0c6f311-a793-4d65-9374-1c0e45f5382c ...
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1answer
124 views

Are there comprehensive alternatives to RSA?

If we wished to, is there a comprehensive alternative to RSA? I say comprehensive as I wonder if there is one which does both encryption and digital signature like RSA? If not, simply what ...
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566 views

bank websites using AES_256_CBC vs AES_128_GCM/CBC [duplicate]

Hello i have just recently started learning about cryptography, so i was doing some little research on what kind of encryption techniques and modes that were used in bank web pages. I have noticed ...
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Should I authenticate memory data which was loaded from authenticated disk file?

Encrypted fields are loaded from disk file to process memory only after file's HMAC validation is successful. Data is still encrypted in memory and will be decrypted later, on demand, when it needs to ...
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Why is PuTTYgen-created RSA public exponent(e) not in {3,17,65537}?

As far as I know, RSA public exponent(e) should be one of {3,17,65537}. However, I found PuTTYgen-created RSA public exponent(e) is 0x25(37) by default,as follows, (PuTTYgen version: 0.66) I am ...
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Does CP-ABE have any disincentive to share secret keys

I want to use a CP-ABE scheme to encrypt data to be accessed by multiple unknown (at time of encryption) users. Reading the papers related to CP-ABE, there does not appear to be any disincentive for ...