Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.

learn more… | top users | synonyms

0
votes
2answers
107 views

RSA decrypting of a huge file by parts [closed]

I need to decrypt a huge file that I own previously encoded by myself with a RSA public key (it's possible for this step using a symmetric algorithm key). Problem is that I can't load it in my ...
5
votes
2answers
2k views

Why is asymmetric cryptography bad for huge data?

I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length. Why is this? I know about hybrid encryption, which uses symmetric encryption to ...
-2
votes
2answers
65 views

Python KDF - Master Key and Derivatives

The encrypted file can be opened by following combinations (either any 2 DK, or 1 MK): DK1 + DK2 DK1 + DK3 DK2 + DK3 DK1 + DK2 + DK3 MK Any heads-up with Python ...
3
votes
1answer
176 views

Why must IV be sent with each packet?

I was reading about Encrypt-then-MAC and everywhere I go it seems people include the IV with the ciphertext generated for each message then MAC that and send all the information concatenated. Why do ...
2
votes
2answers
90 views

Comparing two values without revealing them

Suppose Alice wants to prove to Bob that t1 is less than t2. t1 and ...
0
votes
1answer
76 views

ECDSA: Retrieving non-random k [duplicate]

I have a question regarding the random $k$ number of ECDSA encryption. As far as I know, it is possible to retrieve $k$ (and thus the private key) from two signed messages if both used the same $k$. ...
13
votes
3answers
8k views

Can you help me understand what a cryptographic “salt” is?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can anyone offer me a ...
76
votes
20answers
10k views

Time Capsule cryptography?

Does there exist any cryptographic algorithm which encrypts data in such a way that it can only be decrypted after a certain period of time? The only idea that I can think of, is something like this: ...
8
votes
3answers
13k views

RSA encryption with private key and decryption with a public key

When using the RSA cryptosystem, does it still work if you instead encrypt with the private key and decrypt with the public key? What about in the case of using RSA for sender authentication?
1
vote
0answers
106 views

RSA encryption and signature padding flaw

This is Oxford's computer security exam question: Suppose that Bob has published an RSA encryption key $ke$ (retaining in secret the corresponding decryption key $kd$), and Alice has published a ...
1
vote
0answers
105 views

Is OAEP reversible?

Given nothing more than some integer $m =$ OAEP($M$), is it possible to recover the original plaintext $M$? In other words, without being given the hash functions or the random string used for ...
0
votes
0answers
216 views

Blum-Blum-Shub Cryptosystem

I am given $N$, which is Bob's encryption key. I was able to successfully factor $N$ into $N=p*q$. Alice encrypts a messages for bob and sends $a = [1,1,1,0,0,0,1,0,1,1,0,...]$ $b = 1545164156...$ ...
3
votes
1answer
86 views

What is a Message Transmission Scheme?

I've been given as an exercise to show an encryption scheme that is CCA-secure but is not a secure message transmission scheme. What is a message transmission scheme, and how does it differ from a ...
2
votes
1answer
152 views

ASCII: weakness

Suppose I have an encryption function $e$ of a symmetric cipher with plaintext space $$\mathcal{M}=\{1,2,\ldots,2^{24} \}.$$ Now, consider a list $L$ of integers: $$67, 114, 121, 112, 116, ...
1
vote
1answer
132 views

Help in understanding exactly how lattices used as one way functions for hashing

I am doing a cryptography course via long distance and we have been given an assignment which is based on lattice-based cryptography. I have spent the majority of the past week sifting through papers ...
0
votes
0answers
37 views

Encryption of numeric value using playfair

I am studying in CSE and in my recent exam paper, A question was asked as: Construct a playfair cipher for Plaintext: semester5 and key:technology. Generally as we are taught yet, there is no ...
1
vote
0answers
73 views

El Gamal encryption scheme and symmetric encryption scheme

Consider the El Gamal encryption scheme, a symmetric encryption scheme (KG,E,D), and the following hybrid encryption scheme having an encryption algorithm that, on input a public key (G,q,g,h), where ...
-2
votes
0answers
91 views

Symmetric-Key Based authentication [closed]

So i've managed to answer all the other cryptography questions, but I have not come across this exam style question before, and need help.
1
vote
0answers
78 views

Commutative Encryption with RSA scheme?

I wanted to know how I could manage to do what I'm going to tell you next, with the RSA encryption/decryption scheme. So Alice and Bob each have a public key $(n, e)$ and a private key $(p, q, d)$; ...
1
vote
1answer
69 views

Encrypt HDD with keyfile and password and allow backing up the keyfile with secret sharing

I want to: Encrypt my whole HDD with a keyfile and a password (meaning that both are required to decrypt it), Be able to back up pieces of the keyfile in several distant locations using Secret ...
1
vote
1answer
79 views

Question about dual system encryption

Recently, I have been reading some dual system encryption papers. In these systems, is the adversary able to generate “semi-functional ciphertexts”?
1
vote
3answers
93 views

Encryption time in ECC

In RSA, encryption time is usually much less than decryption time due to having a small public exponent. Can this be achieved in Elliptic Curve Crypto (ECC)?
-1
votes
1answer
81 views

Use of Different keys with PCBC

Currently I am having a doubt, while making a "DES PCBC" encryption on an image I observe a bit of the silhouette of the image (Probably because of the XOR between plaintext blocks and ciphertext ones ...
0
votes
0answers
61 views

AES/CBC fixed Initial vector use-case [duplicate]

I am using AES/CBC to encrypt my http cookie. I never encrypt the same cookie value twice so my understanding is I don't need to use a random initial vector - using a fixed initial vector is fine for ...
0
votes
0answers
47 views

P = NP security implications [duplicate]

If someone finds an efficient way (ridiculous or not) to turn NP into P (such as creating multiple universes, saving the one with the correct answer), would we have any good algorithms for encryption, ...
1
vote
3answers
137 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 ...
0
votes
1answer
81 views

How can I process data within a cloud securely?

I'm new to programming and I'm getting ready to design a proof of concept for an app that I'm thinking of building. Problem is I'm a complete noob to cryptography and need a little nudge to point me ...
4
votes
2answers
236 views

Update to “Cryptographic Right Answers”

I'm a big fan of Colin Percival's "Cryptographic Right Answers" post. This was written in 2009, which is a long time ago in Internet years. Is the advice still valid or, if not, can someone point me ...
2
votes
2answers
204 views

Choice of MAC and handling it correctly

I have recently learned that Encrypt-then-MAC is recommended when using symmetric encryption. I have two closely related questions related to that, which is why I am posting them as one: Looking ...
2
votes
1answer
130 views

Security of the iterated Hill Cipher

I can understand that the basic Hill Cipher is susceptible to known plaintext attacks, but suppose the Hill Cipher is modified into the Iterated Hill Cipher. For a plaintext $x_0=m_0$ and an ...
-1
votes
1answer
49 views

How small are we talking about when defining the small public/private key exponent [duplicate]

I've been wondering about the 'small' part of the attacks on RSA, like the small public key exponent and the small private key exponent and what's not really clear is how small are we talking about? ...
2
votes
4answers
156 views

Construct an encryption algorithm using hash function [duplicate]

We know that Cryptographic hash function is generally a one-way function where we can't retrieve the original message. On the other hand, encryption is a two-way-function where we get the original ...
-1
votes
2answers
216 views

Decrypting Triple-DES using 2 keys in crypto tools

I'm currently working on crypto tools to encrypt/decrypt 4 blocks of messages using Triple-DES with 2 keys. So, I've reached the final cipher text, but now I have to do the reverse and get the ...
1
vote
1answer
94 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 ...
-1
votes
1answer
44 views

The improvement of the private key exponent in the M.Weiner Attack

I am working on attacks on RSA and came across the M. Weiner attack. The limit for $d$ in order for the attack to apply is $d <= (\frac{1}{3})N^{0.25}$. The paper states that Boneh and Durfee ...
1
vote
0answers
54 views

Want to use ECC but am clueless [closed]

First off, I'm not an experienced cryptography or computer person, please bear with me. I have some basic experiences with PGP software though (not much of a redemption huh?). I have some data that ...
6
votes
3answers
399 views

Is the logic for how the enigma machine worked documented somewhere?

I know that there is a formula to calculate the result of any input but is the logic of how the machine actually worked documented? I have seen schematics for the circuitry and even a how to make ...
11
votes
3answers
37k views

How secure is AES-256?

The cipher AES-256 is used among other places in TSL/SSL across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although ...
2
votes
1answer
98 views

Some questions about encrypting (AES) a file with password

I'm relatively new to encrypting, and I have some questions. I intend to write a standalone C# program that will write and read an encrypted file with sensitive data using a password entered by the ...
10
votes
4answers
516 views

Is there an intuitive explanation as to why only the private key can decrypt a message encrypted with the public key?

I have just learned about using PGP/GPG for email encryption and one thing has always bugged me: How is it possible that a message encrypted with somebody's public key can be decrypted only with that ...
-2
votes
1answer
48 views

How to write the encrypted message after using RSA

I have created a RSA encryption/decryption program but how do i write out the results after doing a encryption? Right now I have it so that it will just print out the decimal value of one character ...
5
votes
2answers
215 views

Generating Encryption Keys from Biometric Fingerprint Templates

How would one go about generating Encryption Keys from Biometric Fingerprint Templates extracted from a fingerprint using either Griaule SDK or DigitalPersona SDK or any other SDK that will return the ...
2
votes
1answer
61 views

Why would splitting a password output be better than separate HMACs for encryption/authentication key derivation?

In a recent question I asked here on crypto.se, an answer was given that surprised me a bit. As mentioned in the referenced question, I'm looking to derive encryption and authentication keys from ...
-1
votes
2answers
97 views

Journals to read in order to keep up to date with interesting research [closed]

I'd love suggestions from crypto.stack as to academic journals to read. They can range from introductory to advanced, as long as it's free (requires no access fees). Feel free to edit this question ...
2
votes
1answer
84 views

How does CBC work with read-write volumes?

I have read an article about an attack on LUKS in CBC mode and had a look at the WP article about CBC and now I am confused. If I have understood that correctly then changing the plaintext of a block ...
3
votes
1answer
258 views

Calculating amount of time for brute forcing ciphertext depending on the size of the key

I am a graphic design student and for my information graphic project I have chosen the topic of the history of encryption and how the security level developed over the centuries. It’s basically an ...
2
votes
1answer
103 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 ...
2
votes
1answer
125 views

Is AES-256 over AES-128 weakening the original encryption?

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES-128 and is (probably) outside of my control. If I separately ...
1
vote
3answers
141 views

Is it possible to find data which makes sense when decrypted with different keys?

In theory, does a piece of data exist which, when encrypted (using any method) with a given key, makes some sense when decrypted with the wrong key? Here, a definition of "some sense" might be ...
4
votes
1answer
115 views

Hide message length in symmetric key cryptography

Is there any way to hide message length from adversary in symmetric key cryptography? Suppose we want to hide message length from active and efficient adversaries.