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

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5
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1answer
120 views

Is Django's approach to password reset tokens secure?

I am implementing a password reset feature for a web application and am contemplating adopting an implementation similar to Django. In a nutshell, Django creates a token who is comprised of a ...
1
vote
1answer
77 views

Check HMAC after completing decryption or before?

I have written a piece of software that symmetrically encrypts big files (multi-megabyte). Plaintext is encrypted, after the encryption the HMAC is calculated and written into the header of the file. ...
2
votes
0answers
34 views

Using RSA-SHA as/instead HMAC in OpenVPN?

While reading the manual of OpenVPN 2.3, I came across the --auth alg option. The manual says: Authenticate packets with HMAC using message digest algorithm alg. (The default is SHA1 ). HMAC is a ...
1
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1answer
21 views

Detect if AES and hmac keys are invalid

I have a server which has a configured value of aes and hmac key. The client also should have the same aes and hmac key value. When the client sends a request, the server interprets this request and ...
1
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0answers
42 views

How can I use session salt for encrypting data using AES in CTR mode?

I have to implement a crypto-plugin in Java. The approach followed is conceptually similar to that used for SRTP. The algorithm used for data confidentiality is AES in CTR mode (I'm following a ...
0
votes
1answer
31 views

Should I stretch the secret key in a secure cookie protocol implementation?

I'm building an api authentication layer that basically works like the secure cookie protocol, where instead of a cookie I give the api client a token which they must provide on subsequent requests. ...
2
votes
0answers
52 views

API Keys for REST [migrated]

So I'm developing a RESTful API, but I can't for the life of me understand how API keys work. I'm using PHP, which has an HMAC function, which I've read is a good way to sign requests, but what I ...
1
vote
1answer
64 views

Request signing for REST API

I am building a REST API that will receive requests like: GET /api/entities GET /api/entities?filter=X&sort=Y This seems straight forward: have the client HMAC(path + query, key), send me a key ...
0
votes
1answer
34 views

Signing (HMAC) cookie identifier

Related to this other question about sharing the secret to sign the cookies, my question is more trivial: how really secure is to sign a simple cookie identifier? In example, expressjs#session ...
0
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0answers
36 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. ...
5
votes
2answers
96 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 ...
0
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0answers
38 views

Securing REST API with HMAC and SPA

I'm developing a JS based SPA and the backend is a rest api which uses HMAC. The site/app doesn't have the concept of registered users but it has the concept of session. How do i make sure that the ...
0
votes
0answers
22 views

How to help devs use HMAC safely with multiple data values?

I work on an open source web app framework whose users (developers) need to generate "security tokens" (MACs) for various purposes. Since they've traditionally been using vulnerable methods like ...
1
vote
0answers
58 views

HMAC authenticated API calls with multipart/form-data file uploads

We have an existing API where 3rd parties can push data. The API calls are authenticated with HMAC using the same scheme as described in Ruby's ApiAuth library which I use to verify signed requests. ...
3
votes
1answer
141 views

Generating secret keys with secret keys

Hydra is a secretive organization. It is comprised of several Directors at the top, and many Agents underneath them. A Director sends Agents on secret missions. During these missions, communication ...
2
votes
0answers
64 views

Securing a JavaScript app with RESTful backend

I went through the question Securing a JavaScript Single Page App with RESTful backend that has discussions / options around securing a Javascript client side app that invokes RESTful APIs. However, ...
2
votes
1answer
40 views

What is the ideal HMAC message format if message is an array?

I'm using HMAC exactly as intended to verify the integrity of a message. However, the message is really an associative array (or a hash). Since this will be done on various platforms (within and ...
2
votes
1answer
83 views

HMACs that have the same key and message

im using HMACSHA256 to generate the hash of password and store it. the objective here is to just authenticate users, i.e - save their hashed passwords, and validate users whenever needed using the ...
1
vote
2answers
86 views

Does using a MAC for encryption remove the need for PKCS7 padding with this class?

I am working with this PHP encryption class using MCRYPT_RIJNDAEL_256 and MCRYPT_MODE_CBC with a fixed 32-byte (64 character) HMAC key, as my basis. The class is a result of previous discussions and ...
5
votes
2answers
699 views

Securing a multi-tenant, multi-database REST API

I am looking to improve the security of an existing REST API accessed over SSL. The web service is multi-tenant, such that each tenant has an assigned TenantId. The problem I facing can be summarized ...
0
votes
2answers
236 views

What's the difference between HMAC-SHA256(key, data) and SHA256(key + data)

Is there anything different about how secure these two hashing algorithms are? Does HMAC "fuse" the data and the key in a special way that's more security-aware?
1
vote
2answers
129 views

HMAC and non-repudiation

This was a question on an exam: Two persons are using a one way communication channel and the HMAC functionality (concretely HMAC-SHA1). Choose the correct statement below: 1) We can prove who the ...
3
votes
0answers
302 views

Using HMAC to generate secret keys

I am developing a platform that uses several secret keys for several usages: key1 for hashing passwords (using pbkdf2-hmac-sha256), key2 to generate non-repeating unpredictable uuids (using aes-128 ...
1
vote
1answer
98 views

HMAC + AES to guarantee secrecy and integrity?

As an exercise, I am writing some code that accepts a list of possibly secret properties (e.g. user ID, password, IP address), adds a timestamp, encrypts it, and signs it. Here's a high-level ...
0
votes
1answer
277 views

Authentication and security of a REST API

Scenario: I design a REST API where authenticated users can hit the API over TLS. I have to use TLS as the data transmitted over the wire is sensitive. I don't need authorization right now, but I ...
1
vote
1answer
172 views

Unusual design aspects of AWS HMAC-based authentication, v4

I am designing a RESTful API in python. I want to use HMAC authentication. I could not find any suitable HMAC libraries, so I am rolling my own. However I want to use a well-known standard such as AWS ...
1
vote
2answers
75 views

Is it secure to split information into multiple packets?

I just stumbled upon this SO question. I was wondering if it would be still secure to split the encrypted packet into multiple packets, which are then transferred over the wire separately. Could ...
0
votes
2answers
158 views

HMAC: How unique does a nonce need to be if the Date is also part of the signature?

In a HTTP scheme where the HMAC-SHA256 signature is sent as part of the Authorization header, and the message input contains: The request method URL Post data Nonce Date HTTP header How unique ...
12
votes
2answers
1k 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 ...
7
votes
1answer
640 views

Is there a method to get plain-text from cipher-text in HMAC SHA-1, given that the key is known?

This is technically not even an attack. We have all the resources at hand, except for the original plain-text. We have the cipher-text (to be converted back to plain-text), as well as the key. The ...
1
vote
1answer
357 views

What is the right way to implement Keyed Password Hashing?

As mentioned in this wonderful link, the way to get a PBKDF2 Hash of a user given password given a password (of course), a salt (generated Cryptographically Secure Random Number Generator. iteration ...
0
votes
1answer
76 views

Does encrypting the message protect it against length extension attacks

Assuming the following HMAC is used : HMACK(M) = Hash(K||M) = H which is "secret-prefix" hashed function. M is the plaintext message , K is the secret key used The ciphertext is generated as follow : ...
1
vote
1answer
63 views

Securing connection between redirect from A to B domain

I'm building special extension ( on domain B ) to the present e-commerce hosted on a domain A. The goal is to redirect user from A to B and back. Similar to technique where user leaves e-commerce site ...
3
votes
1answer
128 views

Encryption and HMAC with the same password

I need to send authenticated ciphered messages by using a single password. Reusing the same (derived) key for the block cipher and the HMAC is not a good practice, I know. My initial idea is to ...
0
votes
2answers
110 views

Should I use HMAC in this situation

I need to store a big message encrypted on a server. What I am about to do is: Encrypt the message with a AES key; (Authentication) Hash the message with SHA512 and encrypt the hash with RSA priv ...
0
votes
0answers
56 views

Using HMAC when sending data through an untrusted server

I have a set up like this: Payment Server (PS) <> Front End (FE) <> Client JS. I need to get some data from the Client JS to the PS, without the FE being able to modify it and have PS prove ...
3
votes
1answer
168 views

How secure is HMAC

I'm a building a RESTful stateless API and I'm using a token for authentication. The problem I'm having is I'm not sure how secure HMAC is. I'm using a JSON Web Token library that let's me encrypt ...
5
votes
3answers
116 views

Why can't a cryptographic hash inside a cryptogram serve as a MAC? [duplicate]

My question is closely related to Why do you need message authentication in addition to encryption? Specifically I am interested in symmetric-key cryptography. I understand that attackers may modify ...
0
votes
1answer
126 views

Node's createHmac function

for the node.js crypto command: crypto.createHmac('this is a test', key); What is node expecting for key's encoding? utf8? a binary buffer?
1
vote
1answer
67 views

Use TOTP to prevent simulating requests

I'm developing an API system which provides functionalities for a game. Currently, we are using HMAC to prevent simulating requests (let's say, prevent hackers from simulating the game) but because we ...
0
votes
0answers
33 views

Authentication for Restful web services [duplicate]

I am building a restful web services. My requirement is that I have to provide authentication for accessing the webservices. First I tried with basic authentication. Which is working fine, but ...
0
votes
1answer
146 views

HMAC based algorithm for publicly sharing authenticated messages

I am trying to design an algorithm for publicly sharing authenticated messages. Obviously, asymmetric public/private key schemes do this, but I want to avoid the requirement that users have to keep ...
2
votes
2answers
64 views

Is the HMAC weakened if a part of the message is part the key?

For example: I am using HMAC SHA 256 to sign an XML file. Part of the file data is a version number. If I append the version to my secret to use it as a key, does that weaken the HMAC? As the version ...
-1
votes
1answer
92 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 ...
0
votes
1answer
487 views

Password Storage with Jasypt StrongPasswordEncryptor vs PBKDF2

We are currently working on authentication for a web application. For password storage, we're using Jasypt StrongPasswordEncryptor with SHA-256 and tens of thousands of iterations. Going into the ...
0
votes
0answers
88 views

Payment Application Integration - Encryption or HMAC

Doing an integration with an online payment provider. Payment provider will be making a web request to my server to provide some information about the basket content. On my end there's no payment ...
6
votes
1answer
112 views

4 bytes authentication problem

I have a classic security problem where Alice needs to prove its identity to Bob but with quite unusual requirements and constraints due to a M2M context. EDITs in bold The communication channel ...
1
vote
0answers
105 views

Allowing third-party clients to authenticate with an app server

I'm working on an app that is planned to be licensed to OEMs, who would in turn offer it as a service to their users.  We would host the app server and the OEM would optionally host the app's web ...
3
votes
1answer
182 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 ...
0
votes
1answer
62 views

Does ASP.NET guarantee the integrity of a page's controls on a post back?

Say you have an ASP.NET page that lists the prices for certain items in labels. I know it's cringe-worthy, but say you took the price of the item from the label on the page to determine what the user ...