A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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3
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1answer
193 views

Is this encrypted information? Why is it in a URL?

There's a vendor who sends us reports full of links to articles. Some of these links, especially ones that perform what I'm guessing is an HTTP verb of some kind, look like this: ...
1
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6answers
4k views

Is this authentication scheme secure?

I want to authenticate a client of a webpage and make sure it is a particular user. Let say that we already agreed on a particular hash (SHA256, actually, which I think is secure enough for this) and ...
5
votes
2answers
147 views

Why is weakness of SHA-1 considered a threat to TLS security

If I understand correctly the role that a hashing algorithm (e.g. SHA-1) plays in TLS certificates is as follows: The hashing function is applied to a subject's public key. The CA then uses their ...
0
votes
1answer
77 views

Is there a way to securely check if a password is one of the most used ones?

So lets's say that a user wants to register to some website. For whatever reason, I want to not allow that password if it is one of the top 100 passwords used on my site (So I'm not checking against ...
292
votes
8answers
54k views

How to store salt?

Nowadays, if we expect to store user password securely, we need at least do the following thing $pwd=hash(hash($password) + salt) then store $pwd in your system instead of the real password. I have ...
-4
votes
2answers
116 views

How to identify this hash?

I have one hash, I know its value, but not its type. Here is it: 6dfb036bf703d75f9bc8219ba1224d876783fa61 I tried something like php -r "echo sha1('abc');", but it gave me another value, so this ...
0
votes
2answers
104 views

Password based Asymmetric Key generation

I am looking for a password based key derivation scheme that results in an asymmetric key pair. I have worked with PBKDF and its variants but could not come up with any way of generating a key pair. I ...
45
votes
4answers
5k views

Is this a self rolled hashing/obfuscation method? Can you recognize the pattern?

A system we're introducing into the organization is not using any traditional hashing function that I can find. I've been assigned to "approve" it by black-box testing. I suspect passwords are simply ...
2
votes
1answer
116 views

How might a PIN based Web authentication scheme work?

I'm interested in implementing PIN based authentication for a web application, similar to what Facebook provides in their mobile web site. Here is the user flow: User visits the site for the first ...
8
votes
3answers
998 views

How can I store a password history to prevent reuse?

I have an application with a user database. The database stores the password using a bcrypt hash with a randomized salt. How can I implement a password history set (to prevent password reuse) in a ...
5
votes
2answers
198 views

Why use MD4 for caching?

ccache is a popular tool for speeding recompilation with GCC and other compilers. It works by caching previous compilations and detecting when the same compilation is done again. The detection is ...
4
votes
1answer
4k views

Rainbow tables/hash tables versus WPA/WPA2

In Wi-Fi penetration testing, is it possible to use rainbow tables/hash tables on WPA/WPA2 networks? Is there an advantage of one over the other? ...
-2
votes
2answers
56 views

Is there a reason to salt instead of enxrypting data? [duplicate]

Is it more secure to: a) Take a password, salt it, then hash it. b) Take a password, hash it, then encrypt it(Using a symmetric algorithm with a large key)
18
votes
4answers
4k views

Have weaknesses in SHA-1 and MD5 ever actually been successfully used in an attack?

Pretty much every guide, how-to, and reference for dealing with passwords and hashing has a warning in big or bold letters stating something along the lines of: SHA-1 and MD5 are NOT secure and ...
12
votes
2answers
2k views

If multiple users on the same website all use the same password, is their password hash the same? [duplicate]

My basic knowledge would assume yes, unless websites somehow include the user name into the hashing function with the password, but I am not sure if this is common practice.
2
votes
3answers
63 views

Why do websites use less effective hash functions? [duplicate]

When releasing, say, ISO files, the websites usually provide the supposed hash of the ISO to compare with, to verify its integrity. Or, to prove that it at least probably wasn't tampered with. But on ...
167
votes
8answers
36k views

Why are salted hashes more secure for password storage?

I know there are many discussions on salted hashes, and I understand that the purpose is to make it impossible to build a rainbow table of all possible hashes (generally up to 7 characters). My ...
0
votes
1answer
90 views

How can I ensure that only the message I sent, and nothing else reaches the receiver?

How do I make sure that the open channel I use to send a message to a specific receiver, is not used by a third party to send unwanted files and compromise the receivers system? Is there a method by ...
151
votes
11answers
56k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
1
vote
3answers
116 views

Signatures for an antivirus

When anti-virus software compares an MD5 signature for malware, does it execute the malware on my computer in order to generate the appropriate signature to compare against? [ORIGINAL QUESTION] MD5 ...
2
votes
3answers
170 views

Parameters for PBKDF2 for password hashing

I use PBKDF2 with SHA-256 to store hashes of passwords. I use the following parameters: number of iterations desired = 1024 length of the salt in bytes = 16 length of the derived key ...
12
votes
2answers
4k views

Estimating the size of a rainbow table

What are rainbow tables and how are they used? Gives a very precise answer about what rainbow tables are and how they are used. I had always confused hash-tables and rainbow tables. My question is ...
0
votes
3answers
96 views

How does encryption force a processor to “pause”?

I'm often told that encryption forces processors to "make a pause" when performing the math to decrypt a hash, which is why brute forcing can take so long. I don't understand what it means for a ...
25
votes
4answers
6k views

Why are MD5 and SHA-1 still used for checksums and certificates if they are called broken?

I was just reading about SSL/TLS stuff, and according to this site (which is rated as A by Qualys SSL Labs), MD5 is totally broken, and SHA-1 is cryptographically weak since 2005. And yet, I noticed ...
36
votes
15answers
6k views

Why do people think that this is bad way to hash passwords?

Well, please tell me, what's wrong with this code: $password = "hello"; $password = md5($password); for($i=1;$i<20;$i++){ $password = md5($password); } It's exactly the same as this one: ...
5
votes
2answers
138 views

Why are we using SHA3-512?

As we know, hash algorithms can be used for authenticity of a message. In my understanding, since the message lengths are too large, we convert it into a hash value using hash algorithms and these ...
1
vote
0answers
112 views

Can password hashing both client side and on the back end improve security if we don't necessarily trust the server? [duplicate]

I want to know if it ever makes sense to hash a password client side and rehash it again on the back end. I've not seen this done before which makes me suspicious as to whether it really does add ...
0
votes
2answers
245 views

Breaking encryption with hash value of password?

Can you break an encrypted volume if you know the source code of the crypto-tool used and the hash value of the secret passphrase? Why is it not possible to just reverse engineer the passphrase ...
-7
votes
2answers
5k views

Is AES slower to encrypt than MD5?

Is this the right interperation of this diagram: http://www.cryptopp.com/benchmarks.html AES/CCM MiB/Second:61 Cycles Per Byte:28.6 MD5 MiB/Second:255 Cycles Per Byte:6.8 And does that ...
0
votes
0answers
15 views

Is encryption with a destroyed key a good cryptographic hash function? [duplicate]

Obviously this isn't something I was going to implement, but it was a question floating at the back of my mind. So let's say that instead of hashing passwords to store in the database, you encrypt ...
20
votes
6answers
5k views

What is a good practical (and sane) way to manage all your passwords for online sites?

I am just a mere mortal that wants to have a somewhat secure way of managing all my passwords. This is something that I have been putting off, but since LinkedIn decided to give away one of my ...
-2
votes
2answers
163 views

How to securely transfer password from a registration page to the database [duplicate]

What steps must be followed to send password securely from the user registration page (i.e. client side) to the server over a non encrypted channel (http) when the user registers for the first time ...
4
votes
2answers
173 views

Location of Password Hashes on a Windows Local Machine?

"Where are the two locations that user's password hashes are stored on a local windows machine?" My place of business asked me this question. I know that the SAM stores password hashes, where would ...
13
votes
2answers
365 views

Can client-side hashing improve after-the-fact security in response to password leaks?

Several questions on this site address client-side password hashing, and none of them admit to any security benefit beyond protecting other sites the user might use the same password for. However, ...
-7
votes
2answers
209 views

What is is the best way to create virus signature database? [closed]

We are thinking to develop a new Antivirus program. The main concern is to create a virus signature database. I want to ask what is the best possible way to add viruses signature in our database to ...
27
votes
10answers
5k views

Could I recover the content of file from its checksum/hash?

Let's say I have a video file that is split into multiple parts. Each piece is 2 Megabytes. I also have a list of the *insert hash name here* for each piece and also for the full file. Now assume ...
1
vote
0answers
39 views

Transmitted sensitive user data

At the moment, I have set up mitmproxy and can record all HTTP/HTTPS communications between the client and server. For research purposes I am looking to find a way to detect potential leakage of ...
8
votes
2answers
103 views

Is there a threshold of bits of entropy below which hashing becomes meaningless?

I just read a help page by a mail provider in which they state that all mobile phone numbers will be stored as a salted hash. This strikes me as interesting, since phone numbers don't contain a lot ...
2
votes
3answers
112 views

Verify password hashed with nonce when the password is already hashed on the server?

I found this picture in the Wikipedia nonce article: To avoid sending the password in clear text and prevent replay attacks, the password is hashed together with one random number from the server ...
1
vote
3answers
147 views

why not use hashed password as password [duplicate]

Why dont we use our mobile phone tho hash a password and then enter the hash on a website as the password ? This way the password for the website would be much more complex. Would this even increase ...
1
vote
1answer
81 views

Protecting email addresses if their hashes are publicly avaliable

I am working on a project, where user email address hashes will be available publicly, and I need to prevent them from being quickly discovered by spammers. The main idea of the undertaking is to ...
2
votes
5answers
9k views

inquiry about SHA1 with RSA for certificate signature

As you all know, plenty of X.509 Certificates use (PKCS#1 SHA1 with RSA encryption) as the Certificate Signature Algorithm for generating the signature of 2048 Bits long. We know that SHA1 hash ...
-5
votes
3answers
81 views

how to know the way in which password was encrypted [closed]

i have a encrypted password basically hashed i don't know what it is some thing like 11dfb34b27f539a5e785b68e529fd470 and i know the password i.e., the plain text but i want to know the way that how ...
1
vote
2answers
95 views

Isn't oAuth weaker than traditional passwords

I understand the need for oauth for programmatic access to apis, etc. whereas passwords are used for more human-level authentication. However when we store passwords, we (hopefully) salt + hash them. ...
0
votes
2answers
65 views

PGP vs Hash functions

What is the difference (in terms of security strength) between checking a package' integrity using pgp and hashing functions (i.e. sha256)? Isn't pgp less secure as the verifier must trust the ...
-2
votes
1answer
55 views

What reasons for implementing reversibly encrypted data are there? [closed]

Excuse me if I am wrong, as I am very new to the field, but it seems that the only reason one should encrypt something in a reversible way is if the object receiving the encrypted data is a person. ...
0
votes
2answers
107 views

Using a hash to encrypt data

Lately, I've been reading about cryptography and thought of a method of using hashes to encrypt data. From what I know, hashes are unique to each object and are one way functions. Encryption on the ...
42
votes
12answers
10k views

Is there any real value in hashing/salting passwords?

I look after a system which holds a lot of "low grade" information, nothing financial but name/address/email etc. Someone has suggested that we up the security from the current in house password ...
1
vote
1answer
88 views

Re-sign Certificate Using Different Hashing Algorithm

Consider a certificate used by a Certification Authority. This is currently hashed using SHA-1. I'd like to keep the same public/private key for this, but hash it using SHA-256. By hash it I mean hash ...
6
votes
1answer
303 views

Who in UK I can report to if I know company is storing my password in plain text?

I live in UK, some time ago I wanted to login to my electric company account to check the bill and such, and I had forgotten my password - long story short I got my account locked and had to call ...