# All Questions

229 views

277 views

### What's the reason for applying the hash twice when hashing with salt?

One of the typical approaches to computing a salted hash is this: hash(salt+hash(secret)) where hash is something like SHA-256 hash function - taking any size ...
164 views

### How hard is to find the operators of an addition knowing the sum of them?

I want to learn whether or no there is a cryptographic primitive,scheme assumption that is based on the following hard problem if it is hard . By hard we mean that we have a polynomial adversary: The ...
131 views

### Idea for secure password hash-likes, is this feasible/usable/workable?

(Hand moved from stackoverflow.com,due to suggestion) Since breaking password hashes has become a new passtime for scriptkiddies, I thought of the problem and came up with a novel(?) idea. store ...
183 views

### Attack vectors introduced by compilers

I have a question about attacks on the implementation of cryptographic code that are enabled by compilation and compiler-optimisations. I am aware of this. Would anyone be able to point me to other ...
313 views

### How secure is my OTP program?

I'm writing an One-Time Pad encryption program, because I got really interested in the idea of " encryption which has been proven to be impossible to crack if used correctly". I'm writing the program ...
982 views

### Why do block ciphers need a non-linear component (like an S-box)?

Why is there a requirement of "Non-Linear functions" as a component of many popular block ciphers (e.g. the S-box in DES or 3DES)? How does it make the cipher more secure? The only intuition I have ...
80 views

### In S/MIME, are the same certificates always used to sign and encrypt messages?

My assumption is that S/MIME almost always utilizes certificates as follows: My certificate can be used to allow people to encrypt messages and send them to me. My certificate (the same ...
132 views

### How does DJB's nistp224 manage to fit compressed points into 224 bits?

DJB's nistp224 program purports to be an implementation of elliptic curve Diffie-Hellman relative to the standard NIST P-224 elliptic curve. To the best of my ...
264 views

### 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 ...
40 views

### SHA-512 hash collisions [duplicate]

Possible Duplicate: Is SHA-512 bijective when hashing a single 512-bit block? Is there any guarantee that there are no collisions for all 512-bit input values for SHA-512 (every 512-bit ...
788 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 ...