# All Questions

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### Ciphers in CBC mode reveal place of change in plaintext

Theoretically, when using a symmetric block cipher in CBC mode, the current block is dependent on the previous block. Suppose one plaintext is encrypted using CBC, and then one bit of it is changed, ...
609 views

### Signature schemes for underpowered devices (8bit microcontroller)

I am currently researching into a small scale home automation system, aiming for cost. The system architecture is basically one master and several slaves which are connected in parallel. Recently ...
2k views

### Known-plaintext attack on Blowfish in ECB mode

The protection scheme I faced recently seems so weak nowadays that a simple exhaustive key search would be enough to recover the user key in an acceptable amount of time (it's OK, since almost no ...
160 views

### Given a certain entrophy per character, how long should a passphrase be to guarantee key strength?

Given an entrophy of 1.5 bits per character, how long does a passphrase have the be to guarantee a key strength of a 128 bit random key? Assuming an alphabet of 26, one character takes log2(26)=4.7 ...
497 views

### May the problem with DES using OFB mode be generalized for all feistel ciphers

There is a problem with using DES as the block cipher in OFB mode, eg: the feedback that goes back into the next round will be encrypted with the same key $k$ resulting back into the plaintext IV used ...
8k views

### Does the IV need to be known by AES (CBC mode)?

I was thinking about this today and thought I should ask. I think I understand IV's enough to say that they are basically the same thing as Salts when talking about hashes. They are there to improve ...
491 views

### How do I generate decryption keys for the IDEA algorithm from the 128 bit key?

I am trying to implement IDEA algorithm in C#, just to learn how it works. I have taken a 128 bit binary key and generated the 52 encryption keys using the following code: ...
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### PBKDF2 when dkLen and hLen have the same size

I was reading RFC 2898 and something is not clear to me. When I use PBKDF2 with SHA-256 and I want a derived key with length 32 bytes (the same length as my hash function output), your derived key ...
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### Is this hand cipher any more secure than the Vigenère cipher?

I know that inventing one's one crypto always sucks, but the problem is that hand ciphers are usually very insecure very slow. This is an attempt to make a relatively secure, keyable, and ...
96 views

### AES encryption algorithm [closed]

What is the amount of decrease in the probability of decrypting a data encrypted using an AES algorithm? (That is by introducing each round out of ten whole rounds, how the probability of decryption ...
1k views

### What is the probability of breaking the AES algorithm?

I am doing a project which requires the encryption to be done using AES. Is it really possible (technically) to crack AES? If yes, please tell me: What is the probability of breaking AES? How ...
233 views

### How to use HMAC for large ciphertexts over TLS

HMAC used to secure chosen cipher-text attacks. if we are encrypting a large file (video) and sending it over TLS for decryption, how server can check MAC for ciphertext when we didn't sent whole of ...

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