# All Questions

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### Password as it relates to various encryption schemes

Suppose you have 2 drives you want to encrypt using different encryption algorithms, as an example: AES256 and Twofish. I am aware that using the same password for both could potentially weaken ...
1k views

### Knowing pre-encryption data, can we find the private key CryptoLocker used?

One of our users seems to have been hit by CryptoLocker. As a result, he has a hard drive full of encrypted files. The ransom-ware claims to have used public key encryption on the files. If we know ...
139 views

### How do I prove that this PRNG is easily distinguished from a random sequence of numbers (modulo m)?

I was studying Crypto, and this question came up. Using a PRG like the multiplicative congruence generator: $b_{i+1} = a \cdot b_i \mod m$ How do I prove that the output of this PRG, or any PRG's ...
174 views

### How to design a cryptographically secure file hosting service

How one would go about design something like Google Drive/Dropbox providing the following features: files are encrypted and decrypted on the client files can be synced between devices the service ...
597 views

### RSA decrypt long messages (javascript)

I am attempting to encrypty/decrypt a long message in RSA using javascript (with crypto-js and jsbn libraries). I posted this on stackoverflow too but I figured someone here on crypto might be able ...
219 views

### Isn't the deterministic property of (EC)DSA a security problem?

From what I read in Wikipedia's article "Elliptic Curve DSA ~ Security", the "deterministic" generation of $k$ can help prevent certain type of attacks (such as the one happened to Sony). However, ...
242 views

### Is there proof to the relation between the gap Diffie-Hellman problem and the the Cha-Cheon signature scheme?

I am trying to prove that: "If the gap Diffie-Hellman problem is easy, then the Cha-Cheon signature scheme will be broken." Can you help me to prove it? Is there any proof to the relation between ...
630 views

### Would it be possible to generate the original data from a SHA-512 checksum?

So, I have a file that is XY Exabytes big. I create a SHA-512 hash from it. Are there any theoretical chances that I can retrieve the original data just from the sha512 hash? Also, are there any ...
249 views

### Is there a companion algorithm for OTP to ensure integrity and/or authentication?

One-Time Padding is (theoretically) perfect encryption algorithm. Let's assume that these problems are solved: Fast generation of independent and identically distributed random variables Perfect key ...
203 views

### Having 4096 bit keys and short (< 256 byte) messages, can I simply use the key as OTP?

Assumptions: Alice and Bob use (cryptographically secure, hardware-rng generated) 4096 bit keys. Each message is encrypted using a new key; meaning: once a key is used, it's destroyed. Alice and Bob ...
920 views

### Open source implementations of Symmetric Searchable Encryption and Order Preserving Encryption [closed]

Are there open source implementations of SSE and OPE? Can anyone please point to sample codes, if available. EDIT If cryptDB is not an option, what other options are available? (Indeed, these ...
119 views