Linked Questions

2 votes
3 answers
10k views

Reversing Password Hashes [duplicate]

If someone got hold of the hashes of all passwords for a website, how do they get passwords from the hashes? As far as I can tell, everything seems to say do a dictionary attack/brute force attack, ...
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  • 37
-1 votes
3 answers
10k views

Is it possible to reverse MD5? [duplicate]

I'm new in the security world and right now I'm studying about hashes. Let's say I have md5(x+q) and md5(y+q). I know the value of x and y hidden into md5. Would it be possible to reverse it and ...
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0 votes
2 answers
298 views

Is it possible to reverse a hashed password? [duplicate]

Is it possible to reverse a password hashed with bcrypt?
user avatar
  • 17
1 vote
1 answer
171 views

Is it possible for someone to reverse my hash function if he has access to the assembly code? [duplicate]

My application is written in C and the password is checked by obtaining the user's input and doing some string/math operation on each character, then the sum of each character ascii code is added up (...
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  • 111
0 votes
1 answer
342 views

Can HMAC leak the password? [duplicate]

Imaging the following pseudo-code: h = hash(sha512) h.input(password) h.input(message) send h, message to client If the user has the hash and the message, and the only missing variable is the ...
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  • 241
0 votes
3 answers
160 views

Why can't we produce original text from sha1 if there is no random salt attached [duplicate]

I have bunch of cat images whose names are sha1 of website where it was posted. Here is an example: 3afec3b4765f8f0a07b78f98c07b83f013567a0a.jpg website: http://www.example.com/image.jpg If sha1 is ...
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  • 3
918 votes
11 answers
299k views

How to securely hash passwords?

If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone? I should point out that this relates only to retrieval directly from the database,...
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  • 71.8k
81 votes
5 answers
80k views

How does hashing work?

I have been interested in Information Security. I was recently introduced to the idea of hashing. What I currently understand about hashing is that it takes the password a user enters. Then it ...
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26 votes
13 answers
9k views

How are hashing algorithms useful if the implementation is public?

I may be misunderstanding, but if I want to use a hashing algorithm such as argon2, what's stopping from someone seeing how it works and reversing what it does?
user avatar
73 votes
4 answers
186k views

Is SHA1 better than MD5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than MD5 for hashing since MD5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
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  • 4,250
14 votes
13 answers
9k views

Couldn't we create a string that produces the same hash as another string in SHA-256?

Let's say we have a separate hashing algorithm called s2 and it would convert Hello into dug84nd8. If we could take the algorithm and just reverse engineer it to generate a string like 8GN492MD that ...
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  • 173
34 votes
4 answers
6k views

Does every hash value have an inverse value?

There are many different hash functions, md5, sha, and others. They take a value V and produce a H via transformation Function(V) = H, where Function is md5, sha, etc. My question is: Does every hash ...
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  • 829
14 votes
5 answers
93k views

How safe is the 256-bit encryption used in bank transactions?

Most of the banks use a 128-bit or 256-bit encryption. What does this mean? Does it mean that the keys used in SSL are 128-bit long or what? If they are the SSL key lengths then 128 bit RSA keys are ...
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  • 1,587
22 votes
3 answers
11k views

MySQL OLD_PASSWORD cryptanalysis?

The password hash used for MySQL passwords prior to version 4.1 (now called OLD_PASSWORD()) seems like a very simple ad-hoc hash, without salts or iteration counts. See e.g an implementation in ...
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  • 20.5k
2 votes
2 answers
55k views

Why can't SHA256 be decrypted? [closed]

From many forums I saw that the SHA256 data cannot be decrypted? If that's really true then hows is the data verified? Whats the use of just encrypting the data? The same question goes for the ...
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