a method for constructing a message authentication code based on a cryptographic hash function.

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116
votes
6answers
45k views

Password Hashing add salt + pepper or is salt enough?

Please Note: I'm aware that the proper method for secure password storage hashing is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. ...
69
votes
5answers
53k views

How and when do I use HMAC?

I was reading HMAC on wikipedia and I was confused about a few points. Where do I use HMAC? Why is the key part of the hash? Even if someone successfully used a "length-extension attack", how would ...
17
votes
1answer
3k views

Why can't I use the same key for encryption and MAC?

I wrote a simple file encryption program as an example of how to do encryption correctly, but after reading a questions about encryption + MAC, I think I made a mistake by using the same key for both. ...
11
votes
2answers
2k views

Timing attack against HMAC in authenticated encryption?

In an answer to another question of mine, it was noted that a class using standard string comparison functions when checking the HMAC in authenticated encryption would make the class vulnerable to ...
-5
votes
2answers
140 views

Protection of online image file (ancient manuscript) [duplicate]

I am going to protect an image file (ancient manuscript) which will be available online for everyone to download. I want to protect the file in these situations: When it's on the server, I need to ...
10
votes
2answers
8k views

Salted hashes vs HMAC?

Most of discussions involving access credentials include references to "hashing salted passwords". Is this another way to referring to the HMAC algorithm or a totally different operation? Different or ...
11
votes
1answer
3k views

Why a symmetric key for HMAC?

I am working on securing a RESTful API and am using the Amazon AWS HMAC model as my guide. I am struggling with coming up with a secure way to store the symmetric keys on my end. What is the standard ...
6
votes
4answers
4k views

HMAC/PBKDF2 vs Simple hashing algorithm for web service authentication?

We are in the process of creating a web service and have been investigating ways of securing it. In reality, the service is likely to get very little traffic and the data is likely to be of little use ...
14
votes
3answers
3k views

What are requirements for HMAC secret key?

I'm creating HTTP REST service which will be available over tls only. For authentication purposes I plan to generate JWT token for every user using HMAC HS256. I need a secret key for HMAC. What are ...
6
votes
1answer
589 views

Should password hashes be encrypted or HMACed?

Assume I am hashing user passwords with PBKDF2, bcrypt, scrypt, or some other secure key derivation function. Are there: tangible security benefits, precedents, and respected research for ...
2
votes
1answer
1k views

When to use HMAC alongside AES?

One of my clients wants to provide an URL to each of his customers to register in a system. This URL would contain a query string parameter with some data (e.g. code, email and name) from his clients ...
7
votes
2answers
578 views

Why does node.js scrypt function use HMAC this way?

According to the documentation, the scrypt hash function works like so: The hash function does the following: Adds random salt. Creates a HMAC to protect against active attack. Uses ...
2
votes
1answer
126 views

MasterSecret expansion into keys

I'm trying to deeply understand the steps during a TLS handshake. I've read this answer (which is btw pretty complete), but I stil got a question about the utilisation of the MasterSecret, in the ...