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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Encryption-then-encode or encode-then-encryption?

I have this question in which I m struggling. I have read in many sites about encrypt-then-mac etc. If the confidentiality for transmission is needed, discuss the feature for the order of encryption ...
3
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1answer
64 views

What would currently make the strongest https connection?

when you look at the encryption websites use you will see that there is alot of diversity, some use 256 bit keys some do not, some use DHE-RSA some ECDHE some use sha 256 some sha1, but my question is,...
3
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1answer
62 views

Does encryption of data/information take place in peer to peer networks like Gnutella, Bittorrent?

Do peer to peer networks like Gnutella, Bittorrent have any encryption system to secure the users privacy or encrypt the file/data being shared? Elaborate please.
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bruteforce on aes 256 cbc mode

i have a series of encrypted text , they encrypted by aes 256 bit cbc mode for every encrypted text there is an iv that i have them also and i know its algorithm is aes 256 bit cbc mode i can ...
2
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1answer
37 views

How to select a good scale for letter frequency in a text?

I needed to use a scale in a code to determine which sentence in a file has been encrypted by a single-character key. The scale that i currently used is: +2 for every occurrence of a vowel or a ...
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2answers
61 views

Security (CPA?,CCA?) in Authenticated identity-based encryption

When I read authenticated identity-based encryption by Ben Lynn, encryption works to send data from user A to user B where: $$a=e(d_{A},B)$$ $$s=H_{3}(Msg,K)$$ $$C=<s,\gamma \oplus H_{2}(a,s),H_{4(...
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46 views

How to encrypt huge data using RSA? [duplicate]

Is there any way to encrypt the huge amount of data using RSA? I was supposed it is possible but when I read some articles what I saw is that, this is bad practice or they say can only encrypt bit ...
3
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1answer
83 views

How can I create pre-determined encrypted results?

I want my encryption results to be the lyrics to Star Spangled Banner. The original text I'm encrypting would be, for instance, the menu to a local pizza place. I know what I want my passphrase to be. ...
3
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1answer
42 views

Concept of “guessed ID” in Authenticated Identity-Based Encryption

In Authenticated Identity-Based Encryption by Ben Lynn, in Proof of Integrity (section 4.3) and Proof of Security (section 4.4), I cannot grab the concept of "guessed ID" . Because encryption differs ...
3
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0answers
1k views

Cryptography behind the Turing Imitation Key (TIK)

When browsing the internet I found out about this amazing phone. Well, it would be amazing if it was actually obtainable. It's called the Turing Phone, and it is supposed to come with as good as ...
5
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1answer
676 views

Encrypting user data with their password?

I had an idea once that all of the user data (including the username) could be encrypted with the user's password. Obviously, most sites would store different data, so using the same password and ...
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19 views

How to calculate how many trials I need to guess the plain text if a simple P-Box is used to make the cipher text

If I have 64 bit as input for a straight box that use a transposition process to encipher the plain text and the given 64 bits contains 60 bits as (1s), then how many trial I should do?
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22 views

What do Quantum computers mean for security? [closed]

I know that Quantum computers can speed up brute forcing a key by a ton, but how much? And what does that mean for privacy? Does this just mean that the FBI's side of that court case has won until the ...
5
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1answer
111 views

Encrypted firmware

I have seen many papers on "encrypted firmware" (for example, firmware on Apple Watch like devices) . Can you tell me how it works? Is there a stub in the firmware which is not encrypted and can ...
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0answers
11 views

Can using a cascade encryption decrease security? [duplicate]

When using cascade encryption, can you actully decrease the security, for example if you do something wrong, or is it only depend on which algorithm or mode of encryption you use?
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Why the light contrast of a set $\mathcal{E}$ of VCRG produced by an encryption scheme for a binary image B is defined as follows

In the paper “Image encryption by multiple random grids”, Shyong Jian Shyu, 42(7):1582-1596,· July 2009, the light contrast of a set $\mathcal{E}$ of VCRG produced by an encryption scheme for a binary ...
4
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1answer
48 views

Ideal way to profile/performance-measure cipher implementations

I have implemented a bit-sliced version of two ciphers (Gibbon-120 and Hanuman-120, both part of the Primates family of ciphers: http://primates.ae/wp-content/uploads/primatesv1.02.pdf ) I now want ...
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0answers
56 views

Why can't current quantum computers break RSA? [duplicate]

We have quantum computers and we also have Shor's algorithm. So: Why isn't RSA cracked yet? What are the current quantum computers lacking?
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Did a certain cryptography method get abandoned due to security flaws in the past?

I am researching how quantum computers affect current encryption methods (RSA and more). However, I remember learning in a course that there used to be a particular encryption method which was ...
3
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0answers
28 views

What are the practical impacts of Wassenar Arrangement to crypto development?

Wassenar Arrangement limits transport of high-grade crypto hardware/software since decades, if I don't err. What are its practical impacts in that direction? In particular, does it hinder in any sense ...
3
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1answer
79 views

Highest prime factor that is Safe for a particular scheme

My question is how many bits of prime number is secure so that it cannot be factored from very large number? Until today how large prime factor is found in large number? Quantum computing find ...
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2answers
2k views

What's wrong with XOR encryption with hash and an iterated salt

Suppose you'd use the following algorithm to encrypt a message Let $k$ be the key to encrypt with Let $m$ be the message to encrypt Split $m$ into groups of 512 bytes Given a hash function with ...
3
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1answer
36 views

How does this solution guarantee authentication of B and privacy?

The exercise is: What could be changed on the second message " Kya(Kxb(Ra,Ks)) " to guarantee B's authenthicity and also privacy? My teacher's solution was "add a destination" , so it would be ...
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1answer
54 views

Need help understanding this exercise's solution

We were given this exercise, which asks us to identify the types of keys used on this diagram: The solution was Kxa -> A's private key Kya -> A's public key KxB -> B's private key My question ...
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1answer
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Term for the ratio of ciphertext to plaintext size?

Is there a term that determines the ratio of size of ciphertext $|c|$ and plaintext $|n|$? I vaguely recollect reading it as scale out factor. Is there a better term? Or a popular term for this?
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What are the most appropriate PKI based cryptographic protocols for peer to peer communicaton?

I've been trying to find out which is the most appropriate PKI based cryptographic protocol for peer to peer communication. I do understand that they vary with respect to the peer to peer architecture ...
7
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2answers
390 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
40 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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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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1answer
40 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 ...
2
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1answer
61 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 ...
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58 views

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 ...
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1answer
77 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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1answer
25 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 ...
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1answer
68 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 ...
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1answer
60 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
24 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 ?
3
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1answer
49 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 ...
2
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1answer
73 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 ...
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1answer
73 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
27 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?
4
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1answer
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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
363 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 ...
3
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2answers
606 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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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 ...
4
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2answers
335 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 ...
3
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2answers
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Should I add randomness at the end before AES?

Seen AES, changing a character drastically affects the encrypted 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 <...
3
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1answer
275 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 ...
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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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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 ...