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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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
385 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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2answers
189 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 ...
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2answers
164 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 ...
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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 ...
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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 ...
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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7answers
1k views
How can SSL secure a two-way communication with only one key-pair?
As I understand it, SSL involved the use of a public-private key pair. How does this enable two-way communication?
Suppose I have some server with which I wish to communicate securely. I connect to ...
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1answer
725 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
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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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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2answers
253 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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2answers
299 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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1answer
177 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.
...
6
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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 ...
4
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1answer
185 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 ...
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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 ...
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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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10answers
3k views
Is modern encryption needlessly complicated?
RSA, DES, AES, etc. all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
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1answer
322 views
Does the Biclique attack on AES pose a credible risk to its security?
I have heard a lot about the biclique cryptanalysis research on AES, which as far as I know is the closest anyone has got to breaking AES.
Exactly how close did they get? Does this attack propose a ...
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2answers
715 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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1answer
328 views
Advanced Encryption Standard Algorithm Secret Key
just a follow up question with this question..
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
A 256-bit key can still encrypt a block of plaintext in 128 bit?
but in ...
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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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1answer
180 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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1answer
121 views
NTRUEncrypt - Choose the initial random polynomial
I'm trying to implement NTRUEncrypt but encounter some problems. I've finished all the basic functions that are needed for the scheme base on this Document, but I can't find an algorithm to check the ...
2
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2answers
152 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 ...
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3answers
420 views
Encryption with “constant” initialization vector considered harmful
I try to get the full reasoning behind the above statement. First, after reading articles here and at wikipedia i understand that using an IV only once is good practice.
For stream ciphers not doing ...
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1answer
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How does one implement the Inverse of AES' MixColumns
I got an answer in the related question about Mixcolumn for encryption, but how about decryption?
what will I do?
Because it said that I will used this:
During decryption the Mix Column the ...
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0answers
102 views
Search tool to identify which algorithm is in use [closed]
I'm trying to identify what algorithm is encrypting / encoding / hashing passwords in a client system. I have samples of matching plaintext and ciphertext. Is there a search engine somewhere that will ...
11
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6answers
354 views
Can I encrypt user input in a way I can't decrypt it for a certain period of time?
I run a baseball league and would like to do silent auctions for free agents. This would require teams to enter their highest bid and the highest bidder at the end of the auction period would win. ...
5
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2answers
299 views
Practical necessity of semantic security under chosen plain text attack (CPA) in CBC mode
I was not able to understand why we practically need a CPA security in Cipher Block Chaining. (which insist on having a random IV), let say if the encryption is not CPA secure i.e , the adversary can ...
3
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3answers
817 views
How does the key schedule of Rijndael looks for keysizes other than 128 bit?
It said in Wikipedia that:
[....] Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits. The blocksize has a maximum of 256 bits, but the ...
6
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1answer
379 views
What causes first block of AES decryption to be garbled, even with correct IV?
I am attempting to duplicate wireshark's packet capture decryption for a TLS HTTP session, where I control the private key of the server.
The cipher suite number is 0x00002f, TLS_RSA_AES_128_CBC_SHA
...
4
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1answer
237 views
CBC key lifetime, or, “how big is too big?”
IPSec recommends rekeying SA's figuring in both time and amount of data sent. Even when using AES-256 in CBC mode, the key and IV commonly get re-negotiated after 100MB.
My case isn't using IPSec, ...
2
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1answer
424 views
How to sign a message using RSA?
Assuming I already have a D, P, Q, etc of an RSA key: How do I now sign a message? If it matters – the message is around 100 bits.
I don't know much about cryptography, but I can get these numbers ...
3
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1answer
231 views
Is it safe to encrypt a public key alongside a message with AES?
If I have a message M and a public key P, and I encrypt them alongside one another:
CIPHER = AES(M + P, aes_key)
Is CIPHER now weakened if someone knows what P ...
1
vote
1answer
160 views
ID-Secret Scheme
I have an ID-Secret scheme and I'd like to hear if there are any vulnerabilities present.
Party 1 and Party 2 hold some credentials, an ID and a Secret.
Party 1 Creates this message:
...
2
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2answers
700 views
How can I do a brute force (ciphertext only) attack on an CBC-encrypted message?
Given a CBC ciphertext and IV, how can I find the encryption key?
We are limited with an 8 chars key, each char in the range of [a..h], so I can generate every possible key (these are only $8^8 = ...
2
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2answers
253 views
Simple xor cipher extension
Probably the simplest cipher is the xor cipher with a single integer. One can extend this to use more than one integer by several means. I'm wondering if there is any benefit to doing more than this:
...
3
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2answers
287 views
Can RSA encryption produce collisions?
In RSA, a message is encrypted by $m^e \pmod N$. $N$ is the modulus, $m$ is the message and $e$ is the public exponent. (I know that $m$ should not be greater than $N$.)
My question is, can $m^e$ be ...
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vote
2answers
175 views
One-way function and factoring
I am confused about the hardness of the one-way function behind cryptography -- if someone could factor the large number produced back into two primes quickly then the one-way function would be ...
2
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3answers
328 views
Trying to find a different DES encryption system explanation
I need a mathematical explanation of what does the DES encryption system really do.
This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
3
votes
2answers
7k 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 ...
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1answer
648 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 ...
2
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1answer
569 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 ...
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votes
3answers
302 views
Crypto-Compression Algorithms?
I was wondering, whether there exist such algorithms/enciphering procedures which both compress and encrypt the input data. That means, for starters, the output will be both smaller in size and ...
4
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1answer
244 views
Sites to find crypto intermediate values
Does anyone know of any sites where intermediate values of multiple crypto algorithms (not just the famous ones), including hashes, can be found? I don't just mean intermediate values of encrypting. ...
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1answer
146 views
Which encodings have |encoding key| >> |decoding key|?
I'm looking for an encoding scheme that requires a very large encoding key E (>10MB) and suffices with a relatively small decoding key ...
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 ....
