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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Numeric base conversion in cryptosystems?

I have been wondering if numeric base conversion has ever found an application in cryptography. By base conversion, an example that is probably familiar is Base64 encoding. This is an example of ...
5
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174 views

Does AAD make GCM encryption more secure?

Does AAD make AES GCM encryption more secure? What if we drop AAD in AES-GCM 256? If we drop it, how will it make the encryption less secure?
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1answer
50 views

Why is it that most messages seem to be expanded?

Whenever I have seen a more secure version of a message, the message seems to be expanded by some factor. One example is RSA encryption, but whenever a message does not appear to be expanded it is ...
3
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1answer
53 views

Combining secure hashes with insecure hashes?

Assuming I'm a bank which seeks for secure hash functions to use in the process of signing on digital contents. I'd like to explain / prove why using each one of the following hash functions might ...
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9answers
3k views

Are there any advantages in using proprietary encryption?

Proprietary software generally relies on the fact that in keeping the encryption algorithm private, it gets an extra layer of security implying "Security through Obscurity." Obviously this phrase has ...
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1answer
26 views

Why does OpenPGP encryption produce different ciphertexts from the same plain text?

With the same plain text to be encrypted and the same public key, OpenPGP tends to produce a different ciphertext every time I run the encryption operation. Why is this?
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1answer
22 views

Security Strength of Double Substitution Ciphers

I am wondering why people are using RSA keys when some types of double substitution ciphers seem to be just as secure if not better off. By some types of double substitution ciphers I mean one Which ...
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0answers
23 views

is Authentication tag always appended at last to ciphertext in AES-GCM 256? [duplicate]

I am using AES GCM 256 to encrypt/decrypt a UUID string,We are using java 7 + bouncy castle library for this,We are getting authentication tag of 128 bit ,i am confused ,whether it's position is ...
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38 views

Can a neural network be trained to simulate a cipher?

I believe there are two problems with this in practice: Choosing the components of the network in such a way as to allow them to simulate the operation of the circuitry of the cipher. These ...
3
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1answer
42 views

Insecure third party connection

My organization processes some PII data and shares it with an outbound connection (outflow only) that is a third party. The data transfer transactions occur without human intervention. That outbound ...
0
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1answer
23 views

X509 Cert exploit CA check

Assumptions Let's theoretically assume that a browser skips the check that a certificate it receives belongs to the stated CA (that's an exercise). How could I exploit this in order to impersonate ...
3
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1answer
46 views

El Gamal special construction

The algorithm: I have to determine if the following algorithm is secure: $p,q \in \mathbb{P}$ and $N = p \cdot q$ $e \in [2, N - 1]$ such that $\gcd(e, N) = 1$ $r_1, r_2$ are random numbers ...
0
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1answer
15 views

Is it possible to extract the decryption key from a locked android device

Is it possible to extract the decryption key from a FDE android device while the screen is locked but the phone is powered on. Is the data only safe when the phone is off ?
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1answer
31 views

How to brute force sqlcipher encrypted file with MD5 hash of a 7 bit key?

I have a database file that is encrypted using sqlcipher and MD5 hash. Sqlcipher to my understanding provides 256 bit AES encryption. The key is 7 bits long. How do I brute force it?
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1answer
116 views

How does the ring settings of enigma change wiring tables?

EDIT: The model I'm trying to make is "Enigma 1". I learned initially about it from a book called "Code Book" and then looked at it in detail from its wikipedia page. The site wont allow me too add ...
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0answers
15 views

What kind of hash is in JSON of “Bing image of the day” [on hold]

I just found the json output of Bing image of the day, here it is: http://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1&mkt=en-US I saw a "hsh" json object, and after I checked ...
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0answers
32 views

Exponential cipher theory misunderstanding

Say I pick modulus $m=2633$ and key $e=13$ My private key $d$ is $13$ inverse in $\bmod 2632$ which I need to compute $(e,m)$ is my public key that anyone can use to encrypt message for me and then ...
2
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1answer
119 views

Doubling the block length of a given block cipher

IMHO the main essence of a Feistel cipher of block length $n$ is the working of a non-linear function $F$ that is applied to the two halves of the block of length $n/2$. Now suppose a certain block ...
2
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1answer
40 views

multi key encryption

Is there an algorithm which allows using multiple keys for decryption? I had this scenario in mind: think about being a boss of a corperation which has an encrypted data base with loads of secret ...
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1answer
22 views

Use MDC to provide origin authentication for public key encryption?

Why can't we use an MDC (“Manipulation Detection Code”, as also handled in this Q&A) to provide origin authentication when using public-key encryption?
2
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1answer
83 views

How to detect what crypto-method is used by Filecoder.Q?

I have 2 different images, one original, and one locked by a malware detected by eset as "Win32/Filecoder.Q". How to detect the encryption method that is used and the key, that is not using any ...
5
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1answer
179 views

Full encryption of IDs, partial decryption with customer specific key

I am looking for a "partial" encryption/decryption algorithm. Let's say I am encrypting the following List of IDs (long values) $[1,2,3,4]$ (with a secret key) to an encrypted string $e$, I would ...
4
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1answer
50 views

Can you still decrypt XTS if half of the cipher text is deleted?

If a part of my data is damaged, corrupted, or deleted, is it then still possible to decrypt the rest of the data if you still have the key? The situation: a piece of data (something like a document ...
5
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1answer
307 views

Decrypting an encrypted text out of order

Does there exist a cipher that can be encrypted twice with two different keys and then decrypted twice using either key first? For example: ...
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28 views

What is this encryption type? [closed]

I just get the encryption from some website. Here the encryption output: 1) ZFRSA00013GDU and this is the key before encrypted PKR003 2) YHZSA00100PE9 and this is the key before encrypted PJR011 ...
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1answer
132 views

AES implementation to encrypt files

I'm making a small python program to encrypt an arbitrary text file. Currently I have a file to store passwords (hashed values), so nothing stored in plaintext. The user enters the command line ...
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2answers
4k views

Encrypting and obscuring data between site/user without SSL

Im trying to figure out what the best way to encrypt data sent between a webpage and the user(both ways) is, when hosted in an environment that doesn't support SSL. The purpose of encryption would be ...
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140 views

Verifying Without Knowing Key

Say user Bob sends an encrypted message to a server. People can download the message from this server and later get the key directly from Bob. Is it possible for the server to somehow verify that ...
5
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1answer
311 views

What does 0…0 and 1…1 mean

I am very new to cryptography but can someone explain what exactly does 0...0 and 1...1 mean in general term. Is it that 1st and ...
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1answer
51 views

How to create and validate potential grids when attacking a Playfair cipher?

First up: I am not asking you to decypher anything. This question is about attacking a Playfair cipher; more specifically – how to create potential grids when doing so. I'm currently working on a ...
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How to know the size of an encrypted key that is encrypted using public key

I encrypted a key with a size of 32 bytes. I encrypted it using a public key. How will I know how big is the encrypted key(ciph)? My code: ...
19
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3answers
13k views

How cryptographically secure was the original WW2 Enigma machine, from a modern viewpoint?

If cryptanalysts today were to crack the original Enigma machine, “how fast” or “how easily” could they do it? What methods would they use? The original cracking was significantly helped by operator ...
3
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2answers
593 views

How does blocksize affect security?

I have recently read about how blockciphers and how stream ciphers work, and although I think I finally got everything right, I'm still wondering how increasing blocksize increases security.
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1answer
53 views

Key Hierarchy and key Encryption

If i have two 56-bit DES keys, and I use these two key to encrypt a 256-bit AES key. Like this $K_{AT}$ encrypts $K_{BT}$ and $K_{BT}$ encrypts $K$ What is the effective security of key $K$? Is it ...
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How many possible Enigma machine settings?

I'm trying to calculate the amount of settings the enigma machine has. I have found several sites regarding this topic, but it seems like there are two answers to my question. The first answer is ...
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1answer
115 views

Using e-ID Number for Encryption and Digital Signing

I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this. Generating PGP key-pair ...
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2answers
300 views

Security of the shared secret key for a smart meter (Linky)

Reading the specs of a new electricity smart meter (called Linky in France), I was surprised about the chosen encryption method (128 bits symmetric key AES), based on a single secret key (called CCC ...
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3answers
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Difference between stream cipher and block cipher

A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. A block cipher ...
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0answers
23 views

How to approach to solve cipher text with fixed length key (which is repeating)?

I took a project to solve for lecture. In my project for a given cipher text(length 2031), I have a key (Picture of example is given.) which I do not know the length of it. So I started to try to find ...
3
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1answer
249 views

AES 128 bits with 12 bytes IV vector composed of a 4 bytes counter : safe?

I have a 128 bits AES cypher (GCM, Galois/Counter Mode) using a 12-byte initialization vector (IV) composed of: 8 constant bytes: 6 bytes (device ID) 2 bytes (zero) 4 bytes (incrementing frame ...
0
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1answer
70 views

Should I add randomness at the end before AES?

Seen AES, changing a character drastically affects the ecrypted text. I want to make it harder to decrypt AES I send. So, it seems this can be done by adding some special code and some random bytes ...
2
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Can I serve data for user without the ability to access them? Which functions for the user remain?

My Problem I want to serve sesible data for users as a webservice that is accessed by the user via the browser. Restrictions: I may not be able to technically acces the data of the user Data is ...
17
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3answers
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How to publish a cipher (concept)?

In the last months I was searching for a subject for my bachelor thesis. I came up with an idea for a new cipher concept that works by combining already known techniques in a (hopefully) new way. So ...
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2answers
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Is the one-time pad secure?

I have read about one-time pads (OTP) on Wikipedia. Is this secure? Can I actually use modular addition as ecryption like it said in Wikipedia? And the plaintext is as long as the OTP, so when I send ...
2
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The knife paradox?

In one of the hot forums of today on how to convince friends cryptography is good one of the arguments stated is the knife paradox, I was unable to find the answer on Google and my question is what is ...
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0answers
16 views

Is there a reduction of security if I XOR Pkcs5S2 and SecureRandom?

I'm using this codereview sample to encrypt data. I would like to provide hardware protected encryption and a user password as the key. Is it acceptable to XOR the KDF Pkcs5S2 in Bouncy Castle with a ...
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1answer
38 views

Application level encryption and key renewal

I had posted this question on stackoverflow and been asked to move it to crypto. What is your view on this? What is the doability? I have a question related to encrypting data in the database, at the ...
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0answers
12 views

Fixed initialization vector in aes cbc [duplicate]

What are the pros and cons of using fixed iv in aes-cbc encryption? I've read somewhere that it said using fixed iv doesn't really matter?
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1answer
28 views

Is $E′(k,m)=E(0^n,m)$ semantically secure?

$(E,D)$ is a (one-time) semantically secure cipher where the message and ciphertext space is $\{0,1\}^n$. $E'(k,m)$ is defined as $E′(k,m)=E(0^n,m)$ The question is whether $E'(k,m)$ is (one-time) ...
2
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3answers
130 views

How do I create a secure encryption scheme using addition?

You have a 4 number long PIN code with each number ranging from 0 to 9 which you wish to encrypt. You are then given a random 4 digit number ranging from 0 to 9999, which when added to the original ...