Linked Questions

0
votes
0answers
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 ...
54
votes
3answers
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 ...
18
votes
5answers
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 ...
15
votes
4answers
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?
6
votes
2answers
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 ...
3
votes
2answers
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: ...
4
votes
2answers
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 ...
3
votes
2answers
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))) ...
1
vote
3answers
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 ...
0
votes
2answers
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 ...
1
vote
1answer
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 ...
0
votes
2answers
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 <...
1
vote
1answer
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 ...
1
vote
2answers
70 views

Are there encryption schemes that can be performed using an adding machine?

There's been a lot of talk about encryption that can be done by hand, but what if the user is allowed an adding machine? Let's say addition, subtraction, multiplication, and division are easy. Memory ...
0
votes
0answers
67 views

Understanding birthday attacks on 256 bit hashing and 512 bit hashing [duplicate]

Does it make a difference against birthday attacks if the algorithm that I am using is 512 bit hashing?