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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4answers
146 views

Why shouldn't I store passwords in plaintext? [closed]

Why is it so important not to save passwords in plaintext? I think it is the same issue like authorizing a user on a RESTful webservice, where most developers claim: "Don't send your security token ...
0
votes
3answers
88 views

when to use encoding over hashing?

If encoding is used for integrity someone can tamper it across the network because it is based on some publicly known scheme. When do you use encoding and when do you use hashing for preserving the ...
26
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5answers
4k views

How does storing hash passwords work? [duplicate]

In usual network applications, that employ password hashing, is the user password hashed on client side before sending it to the server, or is it sent without hashing as encryption of plain text ...
46
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9answers
5k views

Why improvising your own Hash function out of existing hash functions is so bad

I'm afraid I'll have tomatoes thrown at me for asking this old question, but here goes. After reading that cooking up your own password hash out of existing hashing functions is dangerous over and ...
1
vote
1answer
29 views

Passing a hash of a secret to a server instead of the plain text

Instead of passing an authentication token or api key in an http header to a server in the plain text, what if I calculated its hash and passed the hash? This way even if a adversary intercepts the ...
5
votes
1answer
115 views

Reviews of Argon2

I am not a security guy but just curious about the things here. I have seen several people in various answers here talked about the password hashing competition. Now that the winner is announced, I ...
5
votes
2answers
92 views

Idea for an encrypted pastebin NON-web application

I have an idea for an app that might be useful (though if it isn't, I've still learned in the process, which is what matters). There are a bunch of encrypted pastebin web apps out there (e.g. ...
39
votes
6answers
16k views

https security - should password be hashed server-side or client-side?

I am building a web application which requires users to login. All communication goes through https. I am using bcrypt to hash passwords. I am facing a dilemma - I used to think it is safer to make a ...
3
votes
2answers
42 views

Incrementing Work-Factor of Hash Functions Over Time

For a long time hash functions have required a work-factor in order to keep the operation "slow" enough to protect individual passwords in the case of a database leak. Bcrypt and PBKDF2 being notable ...
3
votes
1answer
115 views

Two-phase anonymization

EDIT: [N.B: I fully replaced the original question which was not a very good statement of the problem (see comments) with a more apt one.] I have records that contain - among other things - the ...
1
vote
2answers
66 views

Upgrading security of hashed passwords [duplicate]

Let's say we have a database with usernames and passwords, where the passwords are naively secured using a single round of SHA-1 (such as was kinda best practice a number of years ago). Now, let's ...
3
votes
2answers
90 views

What scenario are 'extra' strong passwords and hashing algorithms actually protecting against?

Note: I completely understand the need for strong passwords & I understand that there is an issue of speed with hashing. I am just interested in better understanding the actual negative impact of ...
2
votes
0answers
25 views

The optimal settings of Winrtgen GIU

I'm working with Winrtgen GIU on windows, but I can't fix the right settings to create a rainbow table for a: password length=1-7 Charset=alpha numeric all space What are the ideal values to put in ...
3
votes
4answers
144 views

Is knowing the salt a problem?

I understand that adding a salt would thwart the use of rainbow tables. I don't understand the time it would take to create a rainbow table for a certain salt and of course this is dependent on the ...
3
votes
1answer
63 views

Is appending plaintext to salt equally safe as appending salt to plaintext

Is using hash(salt, plaintext) equally secure as using hash(plaintext, salt), i.e. can the plain text be appended to salt in place of appending salt to the plain text. Why or Why not? What kind of ...
-1
votes
2answers
161 views

Simplest way of hashing a password with multiple different hash algorithms [closed]

I have a list of plaintext passwords that I would like to hash with various different hash algorithms (for educational purposes). As a minimum I would like to obtain hashes under MD5, SHA1, SHA256, ...
3
votes
1answer
102 views

Md5 vs Md4 recognition

Is there a way to actually find out whether a hash is MD5 or MD4? For instance: 10c7ccc7a4f0aff03c915c485565b9da is an MD5 hash be08c2de91787c51e7aee5dd16ca4f76 is an MD4 hash I know that there ...
3
votes
5answers
607 views

Why can passwords be used to encrypt data, but are less strong for authentication?

Encryption software is often password based. Even if the adversary gets your computer they can't get the data without knowing the password, and bruteforcing is infeasible. Websites use passwords to ...
10
votes
2answers
13k views

How weak is MD5 as a password hashing function ?

A professor told us today, that MD5 is weak. I understand his chain of thought but pointed out, that IMHO MD5 is a good way to go if you would use a long (even really long) dynamic salts and static ...
41
votes
3answers
4k views

Security Review - password_hash implementation for PHP

I'm currently working on a "helper function" for PHP's core to make password hashing more secure and easier for the majority of developers. Basically, the goal is to make it so easy, that it's harder ...
14
votes
2answers
343 views

How does SHA3 (Keccak & SHAKE) compare to SHA2? Should I use non-SHAKE parameters?

Keccak is the winner of the SHA3 competition. Since Keccak is highly customizable (presumably for security/memory/time/speed tradeoffs) there does seem to be some controversy around how Keccak ...
3
votes
2answers
116 views

Is signing android apk file with SHA1 digest secure enough?

Google command line example for signing apk files: $ jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore my_application.apk alias_name source: ...
81
votes
10answers
9k views

Is there a threshold for a password so long it doesn't get any more secure or even becomes insecure?

I always hear "A long password is good, a longer password is better". But is there such a thing as a "Password is so long it is becoming unsafe" or "Password is long enough, making it longer won't ...
6
votes
2answers
103 views

Is it good to store passwords in a separate table/database and manage them in a separate process?

I'm quite a newbie at systems architecture and security so I just want to check that this plan makes sense. I'm building a web app and I need to store a password for each user. I've already read ...
-4
votes
1answer
66 views

Sum two SHA256 to get a SHA512 [closed]

I see this code in a web game SHA512(SeedServer + "|" + SeedUser) and I'm trying to reproduce this hash. I tried in PHP: <?php echo hash('SHA512', ...
7
votes
3answers
76 views

Does verifying an additional fraction of a file decrease the chances of collision?

If I have a file of indeterminate length and I generate the SHA256 of that file, then generate the SHA256 of the first half and the last half, then verify all three, does that decrease the odds of a ...
8
votes
1answer
3k views

How can I extract the hash inside an encrypted PDF file?

As long as I know, the encrypted PDF files don't store the decryption password within them, but a hash asociated to this password. When auditing security, a good attemp to break PDF files passwords ...
2
votes
2answers
109 views

Where to store a pepper?

Assuming you're using a pepper in your password hashing, where should it be stored? I know you shouldn't store it in the database since it can easily be found there during a dump and the idea is to ...
30
votes
2answers
3k views

Is it possible to get hacked if my bcrypt hash is publically known?

I just checked https://haveibeenpwned.com/ and I have noticed that I was pwned, therefore I checked the file that hosts the details of my "credentials", however, I see my email in plain text but the ...
3
votes
1answer
135 views

MD5 Algorithm: A basic explanation of the process

Could anyone please explain the basic idea and steps involved in the MD5 algorithm? I tried reading it on the web (Wikipedia etc.), but it was just too high level for me. So, can someone explain the ...
5
votes
1answer
374 views

self-signatures using SHA1

This page says: self-signatures must not use SHA1 You can check this by doing: gpg --export-options export-minimal --export <keyid> | gpg --list-packets |grep -A 2 signature|grep ...
6
votes
2answers
1k views

Can I use SHA-512 hash as AES key?

I want to combine hashing and encryption for better security. So can I use a hash key generated from SHA-512 as a key in AES. For example, I have a password "secret", I calculate SHA-512 hash for it ...
0
votes
0answers
138 views

HMAC Token - Check Logic

I have a situation where I need a token that provides authentication. The common HMAC procedure I found is: Get Some key using login credentials Create Message, append key and other message data ...
2
votes
1answer
64 views

What fuzzy hashing algorithms exist?

I have been trying to find information on fuzzy hashes, and I have found surprisingly little. I know that fuzzy hashes can be used to detect if a piece of malware has changed slightly. I would rather ...
6
votes
2answers
167 views

How is SHA-1 insecure if it is not vulnerable to what MD5 is?

I have been hearing a lot lately about how SHA-1 is no longer going to be used because of how weak and insecure it is, but if it is not vulnerable to collisions like MD5 is, then how is it weak and ...
16
votes
3answers
17k views

openssl: recover key and IV by passphrase

A large amount of files were encrypted by openssl enc -aes-256-cbc -pass pass:MYPASSWORD Openssl should derive key+IV from passphrase. I'd like to know key+IV equivalent of that MYPASSWORD. Is ...
2
votes
1answer
95 views

Is storing encrypted and hashed versions of the same data less secure?

I have some database columns which are encrypted. Obviously there is no way to filter these by plaintext value. As the data stored in the db is ~~salted~~ combined with the IV, there is no way to ...
13
votes
5answers
26k views

SHA, RSA and the relation between them

SHA is the hashing mechanism. However, RSA is the encryption algorithm. So does RSA algorithm use SHA hashing mechanism to generate hashing keys which in turn is used to encrypt the message?? ...
2
votes
3answers
50 views

Pre-generating 'secure tokens'

In our web app we make good use of single use tokens. For example, when somebody creates any of the three "accounts", resets their password, or any other number of things that require random ...
1
vote
2answers
67 views

How can i Identify and use hash function given enough text and their hash?

So, I have this old program currently in use, as i have access to the database i have adopted all data i need except the user passwords.. Now users will provide me with the plain text password and ...
7
votes
1answer
157 views

Increasing the Calculation Cost of Hashing [duplicate]

Is this a secure way to increase the calculation cost of md5 or sha1? public static byte[] increaseHashComplexityMd5(byte[] hash, int loops) { for(int loop = 1; loop <= loops; loop++) { ...
2
votes
1answer
62 views

php's password_hash with system wide salt [duplicate]

I'm thinking about using password_hash function for generating password hashes. I have read that own salts shouldn't be generated and instead use the default one that the function generates. Own salts ...
32
votes
7answers
5k views

How to prevent username and password matches when changing a username?

Let's say that I have a system where one of the security requirements is preventing users from choosing a password that matches their username. Usernames are not case sensitive but the passwords are. ...
1
vote
3answers
82 views

Are hashing functions designed to be injective where the domain is limited to the codomain?

Using the example of md5, I would like to know if md5(h₀) == md5(h₁) for some distinct md5 hashes h₀, h₁. Are hashing algorithms generally designed to avoid this sort of collision? Do MD5, SHA1, ...
0
votes
1answer
76 views

Checking a salted hash against known password?

I've created a mysql dump of my users and passwords and awked them into a presentable form: Passwords: ...
3
votes
1answer
73 views

Can I generate a random 32 bit key by using the Java hashCode and random English words?

I want to generate and communicate a 32 bit key to Bob over a phone conversation. I know he happens to have the same Java and OS installed as I have. Suppose I have a dictionary of 100,000 (English) ...
3
votes
2answers
659 views

Getting reliable checksums

Update: A version of transmission that contains malware has been distributed very recently. Quoting this ars technica article: It appears that somehow the Transmission website may have been ...
3
votes
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
vote
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 ...