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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4answers
279 views
Which block cipher modes of operation allow a predictable IV?
Recently I found out that in the modes CBC and PCBC the IV may be passed in cleartext but never must be predictable. However for this part of my app I rather have the IV be predictable and unique ...
2
votes
1answer
548 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: ...
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 ...
2
votes
4answers
237 views
What is the actual difference between security through obscurity and true encryption?
In an abstract sense, aren't both the same?
Don't their definitions boil down to the following?
security through obscurity:
trying to make sure some information cannot be obtained without knowing ...
0
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1answer
95 views
Digital Certificate Chain Verification
Does a certificate contain the complete chain of all certificates up to the trusted root certificate, or does the program that verifies certificates have to fetch each parent certificate individually ...
3
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1answer
326 views
AES CCM vs CCMP
Are the terms AES CCM and AES CCMP are equivalent, or is there any technical differences between the two?
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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 ...
1
vote
2answers
755 views
Secure private key storage
I'm developing application in Java that has to store RSA keys in software for foreseeable future (that is, at least 10 years).
The two most common standards of storing private keys are PKCS12 and JKS ...
16
votes
6answers
900 views
Is there a secure cryptosystem that can be performed mentally?
I, myself, do not plan on getting into a situation where I would be unable to use a computer in order to communicate securely. However, I can think of many practical situations in which mental ...
5
votes
1answer
111 views
How to turn adversary against encryption of zeroes into adversary against random bits?
I recently read the article Nonce-Based Symmetric Encryption by Rogaway, where he presents two different notions of indistinguishability, which he calls ind$ and ind, respectively. Here's the ...
1
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2answers
160 views
Is it possible to match encrypted documents using user-defined search terms?
Suppose I am storing a number of encrypted documents in a database. I would like to make it possible to identify the subset of documents whose contents match user-specified search terms without a) ...
3
votes
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, ...
2
votes
1answer
110 views
Aes encryption -The relevance of static matrix in mixcolumns operation
Can someone explain to me the relevance of the static matrix used for the mixcolumns operation in aes encryption.i.e the relevance of why the byte is multiplied by 2 + next byte multiplied by 3 + next ...
8
votes
3answers
446 views
What is the best way to put a backdoor in an encryption system?
How can you put a backdoor into an encryption algorithm? Are there any techniques that can be used to reduce the time it takes to break a key?
I am looking for practical examples encryption schemes ...
4
votes
3answers
148 views
Can I jettison MAC if I already have SHA1(M)?
I'm currently using SSL with AES-CBC and HMAC for a file transfer containing string M. Now suppose Alice already knows SHA1(M) (and the adversary does not), and she downloads M from Bob using only ...
-3
votes
1answer
424 views
Advantages of each encryption mode [closed]
What is the advantages of each encryption mode to other encryption mode..
for example what are advantages of CBC to PCBC, CBC to CFB
just like that.
so that I can filter what would be the best ...
1
vote
1answer
918 views
Cipher Feedback Mode
I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC.
Can someone explain to me how CFB works. Such as how ...
0
votes
3answers
182 views
Is there a way to break this encryption?
I was wondering about making up a simple system to encrypt a file:
...
1
vote
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?
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 ...
1
vote
1answer
142 views
Generating a cryptographically secure, many-time use, symmetric encryption key
I need to generate a 256 bit encryption key described by the adjectives in the title. Currently I intend to create the key using this RNG.
Is this a secure manner of creating the key, given that it ...
5
votes
3answers
428 views
Encryption algorithm that produces dummy output on incorrect passwords
Background:
I've been thinking about using encryption in the context of backing up files to untrusted locations (to the point of making the file publicly and widely distributed for practically ...
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 ...
3
votes
2answers
194 views
Is there any recent cryptographic algorithm especially designed for low-level processors?
Most modern algorithms require relatively large amount of resources.
Is there any recent (and freely usable) encryption/decryption algorithm which is specially designed for low-level microcontrollers ...
0
votes
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 ...
0
votes
1answer
319 views
How to hack the new save encryption on ipad for uplink? [closed]
The new iPad version of Uplink appears to be using some new saving mechanic than the PC/Mac Version. Macs and PCs use 'RedShirt' but the iPad appears to instead be using 'SAV62' at the start of saves, ...
2
votes
2answers
598 views
How can I break REDSHIRT / REDSHIRT2 encryption?
Recently, a user on Gaming.SE asked a question about whether the user password in the video game Uplink could be modified after being initially set. The game does not contain an option to change the ...
3
votes
2answers
134 views
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 ...
0
votes
1answer
79 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 ...
4
votes
2answers
226 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. $s = ...
3
votes
1answer
112 views
How to communicate authentication tag for GCM?
I have written some code to do AES in GCM. I currently manually append the tag property to the ciphertext, is this the proper way to communicate the authentication tag?
1
vote
1answer
318 views
AES GCM implementation in c#
I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found here for reference. I'll copy in the relevant portions.
...
3
votes
1answer
160 views
Using a derived key for CMAC
Consider the following authenticate-and-encrypt scheme that uses AES-128 in CBC mode for encryption and AES-128 - based CMAC for authentication:
Two keys are derived from the master key k (16 byte): ...
2
votes
1answer
414 views
Is this design of client side encryption secure?
I want to build a secure file storage web application. Users should be sure that server doesn't know how to decrypt files so encryption should take place at client side (i.e. in Javascript) and TLS ...
4
votes
4answers
1k views
How can one securely generate an asymmetric key pair from a short passphrase?
Background info:
I am planning on making a filehost with which one can encrypt and upload files. To protect the data against any form of hacking, I'd like not to know the encryption key ($K$) used for ...
3
votes
1answer
178 views
How can one share information using the 'host-proof' paradigm?
I am attempting to make a web-based secure password management and sharing utility, both as an academic exercise and to fully understand and feel safe about using it.
I really like the idea of a ...
10
votes
2answers
409 views
Encryption scheme for social-network-like data sharing data via untrusted server?
I am thinking quite a lot lately abut the problem of secure, privacy-preserving social networking. Distributing the network among trusted, preferably self-hosted servers (like Diaspora, GNU Social ...
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 ...
4
votes
3answers
767 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 ...
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 ...
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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
200 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 ...
6
votes
4answers
485 views
Is compressing data prior to encryption necessary to reduce plaintext redundancy?
As explained in William Stallings' Book, in PGP encryption is done after compression, since it reduces redundancy.
I couldn't relate encryption strength with redundancy. Could anyone explain more on ...
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 ...
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 ...
6
votes
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?
1
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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 ...
2
votes
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 $K_2$.
...
1
vote
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?
1
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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 ...
