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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Using username as salt safe enough? [duplicate]

Instead of creating a separate salt generator for each user, can't I just use their username as a salt? It would be unique for everyone, and achieves the purpose of the salts. <?php ...
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Does verifying identity by positions in passwords mean passwords are stored unhashed? [duplicate]

If authentication occurs by asking the user for the characters at certain positions in the password (such as: give the 3rd and 7th character in the password), does this imply that passwords are stored ...
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133 views

Weird 8-character hash [closed]

I'm investigating an application. In a XML file I came across: <ScrambledPassword>U8P3J2N1</ScrambledPassword> I ran it through a hash identification script which is telling me it's a ...
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86 views

How to identify hashes [closed]

How can I indentify a hash? Not with length only, I mean: as I know, specific hashes has specific charsets. Where can I find them? I need this information for making a hash indentification tool. (this ...
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Is MD5 considered insecure?

After all these articles circulating online about md5 exploits, I am considering switching to another hash algorithm. As far as I know it's always been the algorithm of choice among numerous DBAs. Is ...
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0answers
87 views

Line Length Exception in hashcat

I'm very new to cracking a password so sorry if I sound stupid. I am trying to get my admin password from my second PC (I lost it). I did find the SAM file with kali linux and with bkhive and samdump ...
87
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4answers
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Recommended # of iterations when using PKBDF2-SHA256?

I'm curious if anyone has any advice or points of reference when it comes to determining how many iterations is 'good enough' when using PBKDF2 (specifically with SHA-256). Certainly, 'good enough' is ...
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3answers
222 views

How can two parties compare whether a simple (5 letter) shared word matches, without disclosing their word to each other?

I'm having some trouble with this scenario, some advice would be great. The context is that a group of people have each been give a simple 5 letter word - for example: Alice: ACTOR Bob: JEANS Dan: ...
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4answers
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HMACSHA512 versus Rfc2898DeriveBytes for password hash

We are currently using HMACSHA512 in .net, with a 128Char (64byte) validation key The salt is 64 char randomly generated string. We allocated 2048 length on the database for the hashed base64 string ...
2
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1answer
42 views

Personal cipher/digest preferences ignored when generating a new key pair in GnuPG

I have specified personal digest preferences in my ~/.gnupg/gpg.conf: personal-digest-preferences SHA512 SHA256 SHA384 SHA224 SHA1 then, I have generated a new key pair. But when I check the ...
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2answers
52 views

Is there a way to give out secure tickets wihout storing them?

I'm building a website on which I want to make it very easy for users to create pages anonymously and later be able to come back and edit those pages. One way to do so is to give out confidential ...
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2answers
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big O for finding hash of length n O(2^n) or O(2^(n-1))?

note The wikipedia article does not use the big O notation correctly. Thus O(2n) just means 2n attempts I read on wikipedia (CGA) that finding a collision preimage for a cryptographich hash of ...
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5answers
866 views

How secure is it to keep the salt with the password hash? [duplicate]

In Linux we have the salt just next to the password hash in the /etc/shadows file. I always hear that salt value prevents hashed passwords from being cracked by brute force methods. But if somehow we ...
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3answers
71 views

Potential collision with hash password

Normally, the password size is fixed by the hash function in which the password is given right ? Because otherwise, if the password size is bigger than the hash result size, there should be potential ...
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1answer
98 views

How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
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4answers
254 views

Why is a password accompanied by a username deemed 'safer'?

While browsing this community I notice that some people say that the main advantage of usernames accompanied by passwords is as they take more tries to be brute forced, however I don't think that is ...
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3answers
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How to replace an old password hashing method with a newer one in software? [duplicate]

The software that our company builds just went through a security audit. The auditors flagged our use of MD5 for hashing passwords that users can set if they want a password on their files. Having ...
18
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2answers
785 views

Can client-side hashing reduce the denial-of-service risk with slow hashes?

When storing user's passwords that you need to verify against (but not use as plaintext) the current state of the art is: Hash the password Use a salt Use a slow hash function - bcrypt, scrypt, etc. ...
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2answers
88 views

Is there a cryptographic function that generates a reconizable visual pattern?

I have to build a system that will ultimately print a pass allowing access to a building. The validation of this ticket will be done manually (it can also be automatic but that's not likely at this ...
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1answer
56 views

How to change personal cipher/digest preferences of existing OpenPGP key in GnuPG?

The OpenPGP key contains a list of personal algorithm preferences (the meaning of the numbers can be decoded in RFC 4880): # gpg -a --export "foo@example.com" | gpg --list-packets | fgrep 'pref-' ...
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2answers
59 views

Getting the DNS root name servers in a secure way

It doesn't happen often that a root name server changes, but when it does sometimes it takes months for OS vendors to provide patches and in the mean time there is a security risk. So: How to get ...
8
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1answer
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Is every hash format that nginx accepts for HTTP Basic Auth weak against brute force?

According to http://nginx.org/en/docs/http/ngx_http_auth_basic_module.html nginx can read password hashes of these types: crypt(), apr1, SHA1 & SSHA. This is how I understand how these hashes ...
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3answers
103 views

Authenticity of PDF document printed from Word

My MS Word Add-In generates PDF preview of DOCX file on client PC and uploads both files to server. I cannot generate PDF on server. Is there any way to make sure that the PDF is the printed version ...
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5answers
2k views

Is this way of encoding cryptographic hashes safe?

I'm looking at the code of a particular web application that handle file uploads. For some reason, instead of using the cryptographic hash function (SHA-256 in this case), they derive an ID from it, ...
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5answers
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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 ...
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1answer
123 views

Is This DIY Password Authentication Scheme Acceptable?

This is mostly a thought experiment for client/server communication, and I want to know the flaws. When a user account is created (with U as the username and P as the password,) I generate a random ...
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3answers
1k views

How secure are sha256 + salt hashes for password storage [duplicate]

I started reading about password hashing recently on multiple sites like this page on crackstation and others, and for what I have understood, I should avoid using hashing algorithms like md5 and sha1 ...
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1answer
165 views

TLS 1.2 Handshake: How is the ECDHE public key signed by server?

I am dealing with a situation where a cipher option, such as ECDHE-ECDSA-AES128-SHA, is chosen for establishing a TLS connection. In this case, a server, when sending the ServerKeyExchange message to ...
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12answers
4k views

Can a file contain its md5sum inside it?

Just wondering if it is possible to create a file which has its md5sum inside it along with other contents too.
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75 views

Is it worth it to implement both SHA2 and SHA3 at the same time?

I'm creating a password storage system for a web server I'm building for fun. Would it be more secure for me to use both SHA2 and SHA3 for hashing, and then store them in a database? If I use both ...
15
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7answers
4k views

Convenient cross-platform help on checking secure hashes like SHA-256

It is often helpful to be able to obtain a good cryptographic checksum of a file, e.g. the SHA-256 hash. This can be used to verify file integrity, so long as you have a reliable source for the hash. ...
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Does prepending a salt to the password instead of inserting it in the middle decrease security?

I read somewhere that adding a salt at the beginning of a password before hashing it is a bad idea. Instead, the article claimed it is much more secure to insert it somewhere in the middle of the ...
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61 views

Can XOR be used in a Merkle Tree instead of concatenation?

I am trying to understand why, in a Merkle Tree, the concatanation between hashes is used - and not for example the XOR operation. Can they be considered the same for the purpose of a Merkle tree? I ...
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333 views

What steps can you take to make offline cracking of SRP harder?

In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult? My question assumes that your database is already gone and that you implemented SRP more ...
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What is the format of PDF hash?

When I use a tool like pdf2john.py from John The Ripper on an encrypted PDF, it gives me an output like: ...
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1answer
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What hash algorithm is Disqus using now for users' emails? [closed]

Disqus previously used the MD5 algorithm to hash users' emails. A group of Swedes used a dictionary attack to reveal the email addresses (and in many cases identities) of hundreds of Disqus users, ...
5
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1answer
94 views

How does combining SHA256 with RIPE-MD160 compare to SHA256 + SHA-3?

Bitcoin stores its addresses as a combined SHA256 + RIPE-MD160 hash. Is it correct to assume this is done to prevent a failure in the algorithm? Since SHA3 was designed to be an alternative to ...
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33 views

CMS/PKCS#7: specifying signatureAlgorithm with digest?

I'm confused about algorithm selection for Cryptographic Message Syntax (a.k.a. CMS, PKCS#7) signed objects (RFC5652 Section 5.1). The SignerInfo structure (RFC5652 Section 5.3) has two separate ...
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46 views

Designing a security system for road pricing

It's my first semester with Information Security and I still feel a little lost. Sorry in advance for stupid mistakes I may have made. the examples in round brackets below are my own ideas, wrote ...
9
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Gold Standard for password hashing

I've developing a web application that will be dealing with highly sensitive information and I want to ensure the hashing of passwords is gold standard. Ideally I'd go for per-user salted SHA512 ...
5
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6answers
205 views

Is hashing a string a secure manner for generating passwords?

I have several servers that I'm using for an online business. I have passwords for MySQL, Wordpress, SSH, FTP, Domain Provider, Paypal, and many more. I wanted to have a different, very long password ...
3
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1answer
139 views

Is this symetric or asymetric encryption?

I’m at the beginning of my journey into the world of security. I am reading about the most fundamentals topics and I have encountered something unusual that has thrown me. The Conundrum: I have come ...
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3answers
447 views

Any reason not to encrypt a 32 byte value by XORing it with a PBKDF2 hash?

Ordinarily I'd use PBKDF2 to generate a key which i'd use with AES. But seeing as the hash is going to be as long as the data I need to encrypt is there any disadvantage to just XOR'ing it? My ...
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3answers
65 views

What type of hashing method is used for the private key to encrypt for signing messages?

To use RSA for signing, Alice takes a hash of the message, encrypts the hash using her own private key, and appends the result (this is the signature) to the message. Eve can of course still ...
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2answers
116 views

Would my protocol be safe?

Suppose I have a protocol like the one below between users A and B; -A sends random nonce G1 to B -B sends back hash_k(G1) and random none G2 -A verifies hash_k(G1), then sends back hash_k(G1 | ...
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Secure Hash of a very short payload - is it possible?

I am looking to verify the integrity of a very small payload, approx 64 bytes, which will be stored in a QR code. I need to verify that the payload has not been generated or altered by an attacker. ...
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3answers
272 views

Are credit card number look ups more secure with a hash function than with a deterministic encryption algorithm?

I understand PCI DSS 3.0 allows hashes of cardnumbers to be stored separately from encrypted values, but I'm startled at the efficiency of tools like hashcat in discovering card numbers from hashed ...
26
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6answers
27k views

Most secure password hash algorithm(s)?

What is/are currently the most cryptographically secure hashing algorithm(s)? (available in PHP) Speed is irrelevant, because I'm iterating the hash over a fixed time (rather than a fixed number of ...
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Understanding the application of hashes, HMACs, and KDFs

I think that I understand the right application cases for the following crypto functions, but I'd like to confirm my understanding and also propagate the safe use of crypto throughout the intertubes. ...
2
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1answer
154 views

Is there a benefit of using stateless JWT over SHA256 hash for API tokens?

Does it make sense to use stateless JWT (without persistent storage) over plain SHA256? Example scenario: User logs in User token generated as follows: a. JWT.encode(userId, 'secret') or b. ...