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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3answers
109 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 ...
12
votes
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, ...
16
votes
5answers
4k 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 ...
1
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1answer
125 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 ...
9
votes
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 ...
1
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1answer
176 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 ...
23
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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.
1
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1answer
86 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. ...
13
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6answers
2k views

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 ...
0
votes
1answer
63 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 ...
5
votes
3answers
345 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 ...
0
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0answers
56 views

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: ...
-3
votes
1answer
68 views

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
votes
1answer
99 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 ...
2
votes
0answers
42 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 ...
0
votes
0answers
52 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
votes
5answers
2k views

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
votes
6answers
216 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
votes
1answer
142 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 ...
5
votes
3answers
454 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 ...
1
vote
3answers
83 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 ...
0
votes
2answers
123 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 | ...
4
votes
3answers
160 views

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. ...
3
votes
3answers
286 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 ...
28
votes
6answers
28k 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 ...
0
votes
0answers
45 views

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
votes
1answer
215 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. ...
1
vote
2answers
142 views

Is it possible to crack hash with known salt? If yes how?

Hello folks, I was wondering , if the salt in the hash is known to us,then is it possible to crack to extract the password from the hash? If Yes, How?
2
votes
3answers
158 views

Can I initially hash passwords with SHA instead of hashing them with bcrypt to decouple requests from slow crypto functions?

I'm using bcrypt for some web service requests that hash multiple passwords. The problem is that these web service requests can take minutes to complete due to bcrypt. Not very user friendly. My ...
2
votes
5answers
167 views

Does publishing the md5sum of a private key compromise the private key in any meaningful way?

If I have a 4096 DSA private key used for signing binaries, and I want to ensure that a partner has an identical server using the same private key, can I send the md5sum of the private keys over an ...
3
votes
5answers
3k views

Why is client-side hashing of a password so uncommon?

There are very few websites that hash the users password before submitting it to the server. Javascript doesnt even have support for SHA or other algorithms. But I can think of quite a few advantages, ...
19
votes
3answers
3k 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 ...
4
votes
1answer
182 views

What is the best way to store passwords in OpenLDAP?

I would like to store user credentials in an OpenLDAP or similar directory server. A lot of online commentary about storing passwords in modern contexts recommends using password derivation schemes ...
19
votes
2answers
5k views

How big should salt be?

I will be using scrypt to store passwords in my application. As such, I'll be using SHA-256 and Salsa20 crypto primitives (with PBKDF2). Having that in mind, how big salt should I use? Should it be ...
1
vote
1answer
58 views

Are multiple applications of a salted Linux MD5 hash easier to break than one? [duplicate]

I have hashed the same password a lot of times (approximatively 1000 times) using the salted Linux MD5 format. I want to know if it's easier to recover the cleartext password or not. Is there ...
4
votes
2answers
56 views

Secure encrypted storage of values that allows DB lookups?

I'm developing a system that has to store Finnish national identification numbers as securely as possible while allowing "does this identification number exist in the system?"-type queries over a web ...
0
votes
2answers
586 views

Generating authentication token from PHP sessions

I have a traditional PHP site which uses sessions. I've developed a real-time app in nodejs and wish to authenticate users here based on their PHP session. The procedure would go something like this: ...
11
votes
2answers
1k views

Should password reset tokens be hashed when stored in a database?

Passwords are hashed so that if someone gains access to a database of passwords then they won't know what the actual passwords are and so they can't log in. If I can get a valid password reset token ...
2
votes
3answers
708 views

Tracking IP address to prevent abuse without logging user metadata

I am trying to balance good security practices against excessive logging of user metadata / Personally Identifiable Information. I am constructing a web app that allows for secure messaging. In part ...
2
votes
1answer
626 views

This is 2015. Has SHA1 been exploited or cracked yet?

went to Qualys SSL lab and tested one web site. One of the findings says the site is signed with weak algorithm SHA1withRSA and I did some research all are saying we should change to SHA-2. may i know ...
1
vote
0answers
106 views

how many sha1 hashes per time on current hardware [closed]

How many sha1 hashes per second can current hardware (say a 500$ gpu) compute, when the input is 256 byte long? (or any other length). The question behind is how long (or how costly) is it to mount a ...
0
votes
1answer
61 views

MySQL Database Password protection

I am developing an industry-level web server that requires that all passwords be encrypted in some way. The middle-ware for the server is Java-based. My only restriction is that I can't use API's ...
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votes
2answers
92 views

If I were to perform a MD5 hash every microsecond from 1-1-1970 how many hash colisions would I have [closed]

I mean with a standard length of 32 you are doomed to have some hash collision, I ask this question just out of curiosity. I havent put a supercomputer or a timemachine just yet.
3
votes
2answers
898 views

Decoding SHA-512 value

How does the SHA-512 decoder on the following page work? http://md5hashing.net/hashing/sha512#main Hash values supposed to be unable to reverse. Is this page fake?
3
votes
5answers
307 views

A secure way to encrypt a connection between 2 clients securing against both passive and active adversaries

Recently I got interested in encryption and the methods behind them. So for a fun / school project I am building a program in python to encrypt data between two clients (chat and files). I'm just ...
3
votes
0answers
110 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 ...
2
votes
1answer
133 views

Hashing algorithm for cryptsetup

I will encrypt my SSD using cryptsetup and I would like to know which hashing algprithm to use. First of all, cryptsetup benchmark: PBKDF2-sha256 262144 iterations per second PBKDF2-sha512 ...
2
votes
1answer
129 views

Securely storing passwords using PHP5

Starting note: After going through some articles and answers posted on SO related to storing secured passwords I'm still not sure whether my way of thinking is applicable to todays reality. I'm ...
1
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2answers
58 views

Salt addition in hashing? [duplicate]

I may be wrong here but reading about salt I was wondering whether if we use the same salt for every password saved in our database won't users having same password would lead to same hash even after ...