32 views

### AES-CTR key reuse attack with same IV and known plain text [duplicate]

this is from an IT Security exercise which my friend and me cannot solve. Given 2 AES-CTR stream-cipher encrypted files Same known initalizing vector Same (unkown) key Same 128bit Counter ...
91k views

Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
70k views

### How does one attack a two-time pad (i.e. one time pad with key reuse)?

My question might appear the same as the question Taking advantage of one-time pad key reuse?, but actually I did read all the answers and none of them helped me with the details I need. I am new to ...
2k views

### What is the purely mathematical definition of encryption strength?

An encryption function can be used to obfuscate pieces of information and later on retrieve them. What is the yardstick for measuring how well the function encrypts the information ? Given any ...
6k views

### Reusing keys with AES-CBC

I heard that key/IV pairs must not be reused in AES-CTR, or when using any stream cipher for that matter. Yet the attacks described do not seem to apply to AES-CBC. Is reusing the same key several ...
2k views

### AES-256 GCM IV guidelines

If I use for example AES-256 (GCM), and my message is bigger than 256 bit (broken into smaller 256 bit blocks for encryption), should the IV change for every 256 bits of the message?
889 views

### AES 128 bits with 12 bytes IV vector composed of a 4 bytes counter : safe?

I have a 128 bits AES cypher (GCM, Galois/Counter Mode) using a 12-byte initialization vector (IV) composed of: 8 constant bytes: 6 bytes (device ID) 2 bytes (zero) 4 bytes (incrementing frame ...
924 views

### “Weak” implementation of AES-CTR?

Assume an instantiation of AES-CTR like in the following picture: Some details on the input-values for keystream generation: COUNT: a 32-bit value associated with ...
773 views

### (Re-)Using deterministic IV in CTR mode / How to: deterministic AES

I am aware of the requirement of an IV to be unique in CTR mode (Why must IV/key-pairs not be reused in CTR mode?). However I wonder if I can use an IV depending on the plaintext deterministically. ...
349 views

I have a cryptosystem that I'm using for secure chat. It is using AES 256 (with RSA 2048 for key exchange). Would a predictable, and repetitively sent ciphertext plaintext compromise the ...
103 views

### How much data do I leak if I use the first bytes of a file as AES-CBC IV?

I found a piece of code that uses the first 16 bytes of the input file as IV. This immediately set off some flags in my head, but I have no idea how bad it really is. So, how bad is it? Obviously we'...
627 views

### How can I find two strings $m_1$ and $m_2$, knowing that I know $m_1 \oplus m_2$? [duplicate]

Possible Duplicate: How does one attack a two-time pad (i.e. one time pad with key reuse)? I recently started to follow the cryptography class of Dan Boneh on coursera.org and the first part is ...
248 views

### Encrypting/Decrypting sensitive information for storage purpose

I want to store account numbers and routing numbers into SQL database, and i was looking for best way to encrypt/decrypt this sensitive information. After researching i found i can use symmetric (like ...