128 views

### Are 80-bit keys considered secure as of late-2017? [duplicate]

I've seen a lot of ciphers with variants that use 80-bit keys, like Grain, Trivium, KLEIN, KATAN & KTANTAN, Piccolo, PRESENT, RC4, Skipjack, and TWINE. Some of these designs are younger than six ...
23k views

### “SHA-256” vs “any 256 bits of SHA-512”, which is more secure?

In terms of security strength, Is there any difference in using the SHA-256 algorithm vs using any random 256 bits of the output of the SHA-512 algorithm? Similarly, what is the security difference ...
3k views

### How many hex digits do I need to compare when manually checking hash functions?

I sometimes run sha256sum on large files after transferring them from one place to another, and will just skim the hash output to verify it's correct. But, I usually just look at the first/last 5 or 6 ...
3k views

### Which public key cryptosystems are not based on number theory?

Are there any public key cryptographic systems whose hardness assumptions don't involve number theoretic problems?
6k views

### How secure is Salsa20?

I have been hearing about Salsa20 from quite some time. It is even the favorite cipher in the ransomware world. Some ransomware used this cipher, probably because of speed. I want to know how secure ...
9k views

### How insecure is AES-128-CTR to encrypt any kind of data using the Ethereum keystore file format?

I am using the Ethereum keystore file format to encrypt any other data such a plain text or JSON. Here is an example of pseudocode of the implementation: ...
344 views

### Are there valid attacks on full SHA-1?

Google today announced they are sunsetting SHA-1. Its fine by me. But that made me realize I am not keeping up with the research on SHA-1. The Wikipedia page only says Stevens' attack is the most ...
266 views

### Why not use ordinary hash functions for password hashing?

Assume we have a password and add a unique salt to prevent various precomputation attacks. Why don't we do this: SHA256(SHA256(SHA256 ...(Password || Salt))) ...
640 views

### How to explain just how secure AES is in layman terms?

I have a rather particular classmate who wholeheartedly believes that there isn't such a thing as reasonably secure cryptography and that most people can steal encrypted data. I have attempted to ...
2k views

### How to calculate a private key from public key on elliptic curve? [duplicate]

Provided, that you have to multiply a well known G by the private key to obtain the public key, why not keep adding G to itself until you reach the public key. The private key should be the number of ...
322 views

### 80-bit security and attack time

Many designer claimed that their cryptography scheme has 80-bit security. So how to calculate the time of attcking this 80-bit security cryptography scheme, such as 80-bit security RSA using a kind of ...
127 views

### Does this use of hash provide anything over a nonce? HMAC instead?

I ran across some CSRF code that does: Tokens.prototype._tokenize = function tokenize (secret, salt) { return salt + '-' + hash(salt + '-' + secret) } where <...
168 views

### What is the current security level of an algorithm?

I was reading a paper of some years ago about a cryptography and a phrase got my attention. We want to ensure a security level of at least $2^{80}$ I know that $2^{80}$ was used as rule of thumb ...