Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.
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1answer
583 views
What is the difference between CBC and GCM mode?
I am trying to learn more about GCM mode and how it differs between CBC. I already know that GCM provides a MAC which is used for message authentication. From what I have read, and seen code ...
2
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2answers
214 views
AESManaged Trade Compliance Issue in United States
I am currently using AESManaged encryption for my silverlight application. Does AESManaged encryption have a severe trade compliance issue in Bureau of Industry and Security in terms of shipping the ...
2
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2answers
134 views
How can mega store my login details and still be secure?
I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works:
Upon first signing up for an account you make a ...
2
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1answer
212 views
Is AES-256 a post-quantum secure cipher or not?
We know Grover's algorithm speedup brute-force attacks two time faster in block ciphers (e.g brute-forcing 128 bit keys take $2^{64}$ operations not $2^{128}$).
That explains why we are using 256 bit ...
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3answers
135 views
Is there a way to use Shamir Secret Sharing with updatable data?
I want to divide a system that maintains these properties, based on Shamir's Secret Sharing:
A secret key is split up to N pieces, where T of them are enough to reconstruct the key.
The original key ...
2
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1answer
75 views
Individual bits of Textbook RSA
This question relates to the underlying RSA assumption. Forgetting about the fact that Textbook RSA is deterministic, I am curious about the assumed strength of the RSA problem.
Does RSA hide all ...
2
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1answer
227 views
How much extra information is in an RSA public key?
I'm trying to calculate the size of an RSA public key in Ruby. I've retrieved the key in PEM format, and once I've decoded the base64 part from the PEM format, I get the size in bytes. What I find is ...
2
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1answer
194 views
Can ElGamal encryption and ElGamal signatures be used together sharing the same key-pairs?
I'm working on a encryption system where each party can store exactly a single ElGamal private key in a device. This is a hardware limit. The system must be expanded to support signatures and ...
2
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2answers
142 views
Can I save space for short messages by using encryption with private key instead of a signature?
Let's say I have a message, a Private Key and a Public Key.
Normally if you want to see if the message is unaltered and is from the sender you would have the message part + signature part, which you ...
2
votes
2answers
691 views
FIPS 140-2 Compliant Algorithms
Is there any reference to check the list of encryption & signing algorithms which are compliant to FIPS 140-2. After an exhaustive search I could find only "AES".
Any suggestions would be much ...
2
votes
1answer
397 views
Format-preserving encryption implementations
I'm looking for a general, free implementation of Format-preserving encryption
as described in this article and on wikipedia.
Possibly in a well established cryptography toolkit.
My intention is to ...
2
votes
1answer
734 views
In which order are the round keys used during AES decryption?
In the Add Round Key step in AES decryption, which part of the expanded key will I XOR first to the result of the SubBytes step?
Is it the 10th round key?
For example, is this the right order?
...
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2answers
154 views
Algorithm Design for only Mutual Information Sharing
Bob and Alice each have a bit string they want to keep private. They each want to know what the bitwise AND of their two strings would be without telling the other or anyone else listening to their ...
2
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1answer
73 views
Why unit vectors should be encrypted bit per bit in that case?
At this work at section $2.2$ concerning a possible application for the BGN cryposystem the author points out that if you want to encrypt a unit vector $\overrightarrow{u_l}$ of size $l$ then the ...
2
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2answers
147 views
Assymetric password encryption - Viable? Which algorithm?
We have an application that requires cleartext passwords for user authentication because of the authentication mechanism in use (RADIUS/CHAP), which unfortunately we cannot change. Since we don't want ...
2
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1answer
153 views
Encrypting many small messages (log-lines)
What would be the best way of encrypting small mesasages to be stored in encrypted form? (This sounds like somthing a textbook would cover, but I haven't found any references).
Let's say I have many ...
2
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3answers
62 views
Secure communication between multiple peers on a public channel
I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel. With two peers it is easy - they exchange their encryption keys and decrypt the secret ...
2
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2answers
253 views
Perfect security definitions
In my notes, there are 2 definitions of perfect security:
"For $M \in \{0,1\}^m$, define the distribution $D_M$ on strings as follows: to choose a random member of $D_M$, choose a random $K \in ...
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2answers
203 views
Encryption scheme with equivalent keys?
I've long been looking for a symmetric encryption scheme (or algorithm) with equivalent keys. Let me define what I want:
Symmetric encryption algorithm with encryption function $E_k$ and inverse ...
2
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1answer
124 views
Is it OK to use a data-encryption key for key wrapping, too?
Our industry (area of cheap networked devices) has a standard that defines the usage of keys for both authentication and encryption using EAX mode of AES. This standard does not define key management, ...
2
votes
1answer
255 views
Self-expiring symmetric keys, or: cryptography in absence of secure deletion
I can encrypt some data D using a random symmetric key K, obtaining a ciphertext C, and then encrypt K with my public key Pub and obtain H. So far so good: I can only decrypt C if I have H and my ...
2
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1answer
415 views
Is this design of client side encryption secure?
I want to build a secure file storage web application. Users should be sure that server doesn't know how to decrypt files so encryption should take place at client side (i.e. in Javascript) and TLS ...
2
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1answer
78 views
Educational videos for security topics [closed]
Is there anything like the famous "sorting out sorting" video in cryptography/security.
I am looking for some nice videos that explaines SSL, SET, IPSec, PGP, S/MIME ....
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1answer
292 views
Hash or encryption function for challenge-response protocol?
Say I have an authentication protocol where the shared secret is never transmitted. The server passes a challenge to the client and the client calculates a response using an algorithm where the ...
2
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0answers
68 views
How can I prove that this encryption scheme from a random oracle is secure?
I am reading this example:
A random oracle is an ideal object.
What makes a random oracle convenient for proofs is the part about knowing nothing on the output for a given input if you do not ...
2
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0answers
46 views
Encrypting or HMACing password digests
Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect ...
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0answers
190 views
How do I encrypt with the private key? [duplicate]
Possible Duplicate:
RSA encryption with private key and decryption with a public key
This wording is creeping everywhere (e.g. there): "I encrypt with the private key" and even sometimes, ...
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0answers
529 views
MD5 encryption in Windows batch script [closed]
I am making a script in Windows batch to have a registration and login system that stores the passwords in a SQL database using SQLite. I need a command line MD5 encryption program to encrypt the ...
2
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0answers
349 views
Secp256k1 ECDSA test vectors
I`m currently implementing an ECDSA library based on curves like secp256k1. I would like to test it using some test vectors, like ...
2
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2answers
127 views
How to construct a variable length IND-CPA cipher from a fixed length one?
Suppose we can construct a secure (IND-CPA) encryption scheme for fixed length messages. I was wondering if there is a natural way to extend this construction for messages of variable length such that ...
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3answers
473 views
How does one scale encryption strength upwards from 256-bit?
I have seen many examples of encryption up to about 256-bit. But how does one programmatically scale the logic upwards in a language such as PHP or Java to say 1024-bit or even 4096-bit and higher?
...
1
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3answers
284 views
How to submit a new method of encryption?
I came up with a truly new method of applying modulo-2-addition encryption function in stream ciphers which is inspired by a mechanism used to prove a mathematical theorem. How can I determine whether ...
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3answers
266 views
Encryption vs. decryption of same plaintext
Does the same encryption algorithm given the same plaintext always produces the same ciphertext?
Does this cause any security flaws?
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8answers
460 views
Does a public key absolutely need to be used to initiate an encrypted session?
I am a software developer working on an application with the .NET platform. This application needs to provide a secure connection and encrypt all data between the client and the server. It is a ...
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2answers
362 views
Why can't the IV be predictable when its said it doesn't need to be a secret?
I heard multiple times not to reuse the same IV and IV should be random but doesn't need to be secret. I also heard if the IV is something like sequential numbers or something predictable I should ...
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4answers
401 views
Is my pseudo-random initialization vector secure?
How can I know if I am generating a secure pseudorandom initialization vector?
Currently I am planning to generate a pseudo-random initialization Vector using current date and time - is this secure ...
1
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2answers
365 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 ...
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2answers
730 views
How to perform file encryption using 128-Bit AES?
I am confused, how can I encrypt a file using 128 Bit Advanced Encryption Standard?
Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? Is ...
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3answers
201 views
Getting started [closed]
I'm looking for a good place to start in cryptography and places to go to get free books etc on the topic.
I have been looking online but I always get stuck at some point or another. I need something ...
1
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3answers
217 views
How to encrypt data and know it will be secure for at least a few decades?
I want to encrypt a small amount (few kilobytes) of data and be fairly confident it will be secure against brute force decryption and advances in cryptanalysis for at least a a few decades (or more). ...
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3answers
434 views
Which attacks can be avoided by the use of OFB instead of ECB?
For a file encryption program, I was told to use Output Feedback mode (OFB) instead of ECB (Electronic code book) mode.
Which attacks can I avoid by this choice?
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1answer
655 views
Big-O Notation: Encryption Algorithms
I am currently completing a dissertation concerning the encryption of data through a variety of cryptographic algorithms.
I have spent much time reading journals and papers but as yet have been ...
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3answers
349 views
Is public-key cryptography the only option in this scenario?
Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...
1
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1answer
91 views
What's the difference between Trapdoor Functions and Encryption Functions?
From Wikipedia:
A trapdoor function is a function that is easy to compute in one
direction, yet believed to be difficult to compute in the opposite
direction (finding its inverse) without ...
1
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1answer
97 views
How can encryption software accept password lengths which are not one of the AES key lengths?
AES comes with key sizes of 128, 192, and 256 bit.
But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit.
How is this ...
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2answers
117 views
FIPS 140 compliance for encrypted files
Does FIPS 140-2 require specific key sizes, or does it have specific requirements for the data?
In other words, if I encrypt a file, how I can check whether it is FIPS-compliant or not? Does only the ...
1
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4answers
345 views
How easily could this be cracked?
I'm looking into encrypting files like this: First, I SHA-1 hash the password. Let's say the password is something normal like "hello123", and then hashed. Then I encrypt a file using this:
...
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1answer
327 views
Traditional DES scheme in Unix crypt function
In a security context course, we need to reproduce the old DES hashing scheme in the crypt program, on an old unix system.
I am actually reading the crypt page on wikipedia:
The traditional ...
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1answer
258 views
One-time pad and zero key
I'm doing some exercises before my exam, and I am stuck with task number 4 in this file: http://www.cs.umd.edu/~jkatz/crypto/f10/hw1.pdf
Could you help me with this task?
When using the one-time ...
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3answers
167 views
Looking for cipher that uses one ciphertext
I'm new to Cryptography so please free to edit my question for clarity and add the appropriate tag.
I'm trying to research if the following is possible. Suppose
John has a message that he ...
