Questions tagged [algorithm]

Algorithm is a set of step-by-step operations to be performed including calculations, data processing, and automated reasoning.

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535
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11answers
87k views

Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
8
votes
2answers
21k views

Why is MD5 considered a vulnerable algorithm?

I know that MD5 is the most vulnerable hashing algorithm, and particularly vulnerable to Collisions. But the collision vulnerability is not very risky and somebody might use that as an advantage, but ...
36
votes
2answers
22k views

Salted hashes vs HMAC?

Most of discussions involving access credentials include references to "hashing salted passwords". Is this another way to referring to the HMAC algorithm or a totally different operation? Different or ...
15
votes
1answer
5k views

Understanding brute-forcing algorithms [duplicate]

I've been reading up on brute-forcing techniques and possible methods of prevention, but there is one issue that I haven't been able to find a clear answer to. The way I understand it, a 'simple' ...
4
votes
4answers
3k views

For someone who has a key and ciphertext, is it possible to find out what encryption algorithm was used?

For someone who has a key and ciphertext, is it possible to find out what encryption algorithm was used?
1
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1answer
2k views

How to implement iterations when hashing passwords?

To securely hash passwords, algorithms such as PBKDF2 do many iterations of a common hash such as SHA1. Are there certain ways that these iterations need to be done to be safe? In particular, from ...
21
votes
7answers
5k views

Why not mix hashes?

To make hashes harder to target by specialized hardware, I intuitively imagine that mixing a set of different hash algorithms should provide additional strength. For simplicity lets assume Hash1 is a ...
20
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4answers
3k views

Should I use own constants when using well known hashing algorithms?

I understand that it is important to use well known and well tested hashing algorithms instead of designing my own. For such there often are reference implementations available, which initialize the ...
14
votes
1answer
4k views

Why is asymmetric encryption less efficient than symmetric encryption?

It's common knowledge that asymmetric encryption is in general much more expensive to compute than symmetric encryption, thus common practice is to use asymmetric encryption to establish a symmetric ...
33
votes
5answers
8k views

SSH - If Eve has the passphrase and public key, can she derive the private key?

I have used ssh-keygen for creating an RSA 4096-bit SSH private and public key pair. I used a passphrase for the private key. If an attacker, Eve, knows the passphrase in addition to the public key: ...
10
votes
1answer
14k views

Is knowing the decrypted and encrypted data enough to find the key?

Let's say an attacker knows the encrypted content, the decrypted content and the algorithm used: can he get the key that was used to encrypt the content or does it make it easier to find the key out? ...
11
votes
2answers
1k views

Unseen.is encryption claims revisited with their proprietary, patented “xAES” algorithm

I had asked last year about the encryption claims by the web service called https://unseen.is. The very same service that had claims of "beyond army level encryption", "4096 bit keys" etc. This is the ...
8
votes
5answers
988 views

How to prevent pay per show/click abuse?

We have a webapp. 3rd party websites put our banners on their pages (banner is a snippet of HTML). They are paid for it using "Pay per click" or "Pay per show" methods. So 3rd party website's owners ...
1
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2answers
1k views

Is it possible to brute-force the original message of SHA-256 given the size of original string?

Given the SHA-256 hash, the size and the encoding of the original string, is it possible to recover the string via brute force? How many string of a given size will result in the same hash?
7
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3answers
1k views

Is it a good idea to have a “master” password?

Though I do have a good memory of passwords, it is quite impossible to have one password per application. Yet, it should be... My current way to deal with passwords is to have five passwords and to ...
4
votes
2answers
154 views

Securing anonymous website posts

Can a website allow users to securely post anonymously, while still allowing these posts to be edited by the original author at a later time and preventing editing by other users? In this context, '...
2
votes
0answers
143 views

Differential Privacy: understanding sensitivity [closed]

From this link on Differential Privacy, the L-2 sensitivity is defined as follows: Question: Here's my understanding of the above equation: Make a set of D' data sets such that D' is same as D ...