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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Textbook RSA to Realworld RSA
Is there a paper or link where it explains , how the plain vanilla Textbook RSA is actually implemented in practice with all the padding and stuff ?
basically i want to know the intricacies of ...
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1answer
80 views
Using “Additional Authenticated Data” as a secondary key
In implementing a cipher in GCM or CCM mode, you are provided the option to add "Additional Authenticated Data" (AAD). This AAD is required for decrypting the cipher text, and seems to be used when ...
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1answer
112 views
How to communicate authentication tag for GCM?
I have written some code to do AES in GCM. I currently manually append the tag property to the ciphertext, is this the proper way to communicate the authentication tag?
4
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2answers
227 views
Is the encryption of a hash a good MAC?
At university we were told that it is a bad idea to implement a MAC by simply concatenating a key with the data to sign and to run it through a hash function (e.g. $s = ...
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1answer
318 views
AES GCM implementation in c#
I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found here for reference. I'll copy in the relevant portions.
...
3
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3answers
470 views
Which of these 3 AES 128 symmetric encrypt/decrypt routines is most secure?
I am developing a symmetric en-/decryption routine written in c# for a database containing user-specific, sensitive information.
I have narrowed down the implementation to 3 different approaches, ...
-3
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1answer
180 views
Multi layer encryption with ECB mode [closed]
if i use the 2 of the same key with 2 of the same algoritm when encrypting in ECB like when i have 2 blocks of the same color and i encrypt the 2 blocks with the same color the cipher text should
not ...
4
votes
1answer
210 views
I need an opinion of encryption method I thought of in High school
First, I'm really not into cryptography, but have some basic knowledge. This was a thought experiment (and later exercise for my programming skills), but even though it was long time ago and I tried ...
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 ...
3
votes
1answer
160 views
Using a derived key for CMAC
Consider the following authenticate-and-encrypt scheme that uses AES-128 in CBC mode for encryption and AES-128 - based CMAC for authentication:
Two keys are derived from the master key k (16 byte): ...
5
votes
1answer
142 views
How are state wiretaps obtaining plaintext from encrypted transmissions?
According to the US 2011 Wiretap Report, encryption — on the off chance that it is encountered — has been no hurdle to retrieving the content of a conversation.
Public Law 106-197 amended 18 ...
0
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0answers
84 views
How do I protect user data at rest? [closed]
I want to encrypt the username, email, and password fields in the database AND encrypt user files at rest. How can I do this? I am aware of software such as Gazzang and since there is not cost ...
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vote
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 ...
2
votes
1answer
551 views
What is the difference between these AES encryption methods
I am using AES encryption (Rijindael) with Base-64 encoding in Obj-C and VB. I am currently using the following two projects to achieve this:
Obj-C: ...
0
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1answer
118 views
RSA Signature - Multiple Use Weakness
I cite from Fundamentals of Computer Security (Chapter 7 on Digital Signature, Paragraph 7.3 on RSA Signatures, page 289):
Multiple uses of the RSA Signature scheme tend to weaken it. The way out ...
3
votes
2answers
228 views
Is ECB mode secure if plaintexts guaranteed to be unique?
I've got a scenario where I need to encrypt many small (16-byte) plaintexts. I want to use AES-128 in ECB mode. Notably, each plaintext is guaranteed to be unique, though each may differ by only a few ...
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2answers
481 views
Why is ciphertext from low entropy plaintext not compressible?
This comes following a discussion with a colleague.
My plaintext file plain consists of a about 100,000 lines of "all work and
no play...". It's size is: 2.2 MB.
...
3
votes
2answers
100 views
How can the Schmidt–Samoa cryptosystem uniquely decrypt large messages?
Suppose I choose $p=7$ and $q=11$.
This gives a public key of $p^2·q = 539$.
However, decryption occurs using a modulus of $p·q=77$.
If a person chooses to encrypt $500$ using my public key, how ...
2
votes
3answers
278 views
Can I pre-define the points in Shamir's Secret Sharing algorithm
With Shamir's secret sharing is it possible to pre-define the points returned by the algorithm?
For simplicity if I have (k, n) where k=2, and n=4, and I have the points X,Y,Z, and Q. Can I create ...
6
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4answers
1k views
Difference between encrypting something and hashing something
What is the difference between encrypting something and hashing something? in what situations would I want one or the other?
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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 ...
6
votes
2answers
2k views
What's the fundamental difference between Diffie-Hellman and RSA?
What is the difference in the purpose of DH and RSA? Aren't they both public-key encryption?
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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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1answer
129 views
Transparent cipher
I'm trying to implement this protocol:
Alice has her permanent key $K_1$. She computes $E(K_1, P)$.
She wants to share $P$ with Bob, Carol and Dave. For each of them she:
2.1. Generates $K_2$.
...
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0answers
64 views
In S/MIME, are the same certificates always used to sign and encrypt messages?
My assumption is that S/MIME almost always utilizes certificates as follows:
My certificate can be used to allow people to encrypt messages and send them to me.
My certificate (the same ...
0
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0answers
58 views
What is cross-certification [closed]
What does cross-certification mean? Can I program my app to accept all certificates that are cross-certified by a certain CA? How common practice is this?
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1answer
196 views
File Encryption/Decryption in ECB mode [duplicate]
Possible Duplicate:
Removing Padded Value in Decrypted Message
I tried to encrypt and decrypt a file in ECB mode using AES Algorithm but I encountered one problem during decryption, I don't ...
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1answer
397 views
Removing Padded Value in Decrypted Message
How to remove padded value in Decrypted Message?
I am using AES Algorithm..
ex:
this is the decrypted message..
"abcdefghijklmn "
there is a 2 space in that decrypted message which is equivalent ...
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vote
1answer
456 views
How can 3DES encryption use decryption in the middle step?
I have been reading about the 3DES algorithm and I cannot understand one part. In 3DES we do following operation: $$C=E[K_3,D[K_2,E[K_1,P]]].$$
Where $C$ is ciphertext, $P$ is plaintext, $E$ is DES ...
2
votes
2answers
192 views
Is RSA in a ECB-like-mode safe for bulk encryption?
Let's say I would like to communicate with my friend using asymmetric/public-key encryption, e.g. RSA.
(Note: I do realize that in practice this is done through an intermediate symmetric key, but ...
4
votes
3answers
768 views
Are there any simple and yet secure encryption algorithms?
Being very new to C++ and cryptography, I finally managed to implement a version of the Vinegere algorithm. I would like to try something a bit more complicated. I have looked at AES and DES and ...
1
vote
1answer
134 views
Using compression to test encryption
Is the uncompressibility of encrypted data a necessary property for a good cryptographic algorithm?
To make a crude experiment, I encrypted an 8K file with all 'A' and then compressed both the ...
3
votes
2answers
138 views
Is this streamable combination of encryption and MAC secure?
I want to combine encryption and MAC.
For encryption I use AES-256 with CBC and PKCS5Padding.
For MAC I use HmacSHA512.
I use the Encrypt-then-Mac approach (calculate MAC over the ciphertext and ...
5
votes
2answers
165 views
K out of N encryption
A friend just showed me how to combine padlocks to achieve a lock that opens when k out of n people turn their keys.
I was ...
3
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1answer
124 views
Safely use CryptSignAndEncryptMessage?
I am developing an application that sends messages which I want to encrypt and sign. The CryptoApi offers a function called CryptSignAndEncryptMessage.
The description says, what this function ...
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vote
2answers
160 views
Brute force a ciphered message?
I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
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votes
1answer
733 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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vote
3answers
201 views
Does the MixColumns step come before or after AddRoundKey in AES decryption?
I found these images depicting the AES decryption process:
In the first image, the MixColumns step comes before the AddRoundKey step, while in the second image, the AddRoundKey will come before ...
4
votes
2answers
254 views
After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?
Preface: This question was originally asked on Theoretical Computer Science and later on Computer Science. The kind people on cstheory.SE referred me to this web site. It is being repeated here in an ...
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1answer
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2answers
183 views
How can encryption involve randomness?
If an encryption algorithm is meant to convert a string to another string which can then be decrypted back to the original, how could this process involve any randomness?
Surely it has to be ...
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1answer
180 views
Why does my implementation of CBC mode only decrypt the first block correctly? [closed]
I have the following code that uses a CBC mode to encrypt a text by dividing it to 3-elements block. But it only works correctly on the first block which is xored with the IV.
...
4
votes
1answer
186 views
Is it secure to use the hash of key as the IV in AES encryption?
I need to store some sensitive data for a program. For each copy of the program, there will be a unique key for encrypting one (and only one) file using AES encryption (OFB). The key will not be ...
6
votes
2answers
375 views
Hash decrypts key, key decrypts cipher… why?
I noticed recently that a couple of pieces of encryption software (TrueCrypt being one of them) don't directly use a hash of the password as the key for the block cipher. Instead, they generate a ...
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2answers
301 views
What is the time complexity of the RC4 encryption & decryption algorithms?
I'm trying to figure out what the time complexity of RC4 encryption & decryption algorithms is, in big-O-notation.
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0answers
222 views
How to calculate a key for Hill Cipher? [closed]
I need an easy way to calculate 3X3 key matrix to encrypt a 256 characters text ?
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2answers
69 views
Encrypting documents through a proxy key
Suppose I'm developing an app to secure a lot of documents. These documents were encrypted (say, using AES) with a key X.
This key X is basically the password that the user enters before wanting to ...
1
vote
4answers
400 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 ...
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1answer
182 views
ECIES protocol - what does the || operation mean?
I am studying elliptic curves problems, which also includes study of related protocols such as ECIES. A there is a problem I don't understand operation $||$. What this operation mean?
Some stuff is ...
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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 ...
