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

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14 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
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0answers
17 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. ...
2
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1answer
119 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
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0answers
36 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
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1answer
33 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
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1answer
63 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 ...
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2answers
71 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 ...
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2answers
360 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 ...
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2answers
97 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?
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2answers
98 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
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0answers
152 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
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1answer
79 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
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1answer
192 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 ...
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1answer
112 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
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2answers
64 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
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2answers
100 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 ...
9
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2answers
911 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
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1answer
561 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 ...
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1answer
240 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 ...
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1answer
70 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 : ...
0
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1answer
52 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
111 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 ...
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2answers
97 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 ...
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0answers
46 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
128 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
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3answers
108 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
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1answer
111 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
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1answer
61 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 ...
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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
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1answer
130 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
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2answers
58 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
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1answer
81 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
377 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
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0answers
68 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
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1answer
109 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 ...
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0answers
85 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
158 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
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1answer
57 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 ...
0
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1answer
162 views

Using hashed password as secret key for hmac to avoid exchange of secret between server and client

I'm currently trying to improve our API to be more restful, therfore avoid any state on the server. I want to accomplish this with a hmac token, appended on every request. The hmac will be made with ...
1
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1answer
114 views

Should HMAC key be changed regularly? Should it be kept secret at all times?

I am doing an HMAC of some cipher-text, IV and encryption algorithm. Right now I am using a hard-coded key that is known to both sender and receiver. I was wondering if the key should be changed once ...
2
votes
1answer
836 views

HMAC secret key client storage

I've read numerous articles about using HMAC and the secret key for client authentication in a RESTful client (Javascript) application today. Still, I don't find a single source that is able to ...
0
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1answer
91 views

Is this signature methodology secure?

I'm working on authentication for my JSON-RPC API and my current working strategy is using signed requests sent via POST over SSL. I'm wondering if anyone can see any vulnerabilities that I haven't ...
0
votes
1answer
685 views

Openssl ciphers SHA384 and AEAD

When running the command: openssl ciphers -v I get a long list of cipher combinations. I'm having issues interpreting some of them. An example is: DHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=DH Au=RSA ...
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1answer
97 views

Where are MAC used?

I can think of where people use hashes and signatures. But where are MAC used in real life? Are there any protocol in cryptography that uses MAC? Or examples where MACs are relevant?
1
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1answer
332 views

What is a AUTH-KEY in the security of the computers?

I'm studying security in computers and in particular the URL Spoofing. I understand that a form of URL spoofing is phishing. Then I read that a countermeasure against phishing is the authentication ...
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0answers
149 views

Login Authentication with SSL and HMAC

My question is pretty similar to : http://stackoverflow.com/questions/5487757/using-hmac-sha1-for-api-authentication-how-to-store-the-client-password-secure. Basically, I want to write an API for my ...
1
vote
1answer
203 views

Confused about the most relevant way to secure my APIs

I own a Javascript application (Single Page Application) hitting some apis from my own RESTful backend. What I expect for my authentication/(authorization) mechanism is three things: Preventing ...
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0answers
150 views

Gladman's file encryption library = AES in counter mode with HMAC-SHA1 authentication?

I would like to use Gladman's algorithm to create AES encrypted data in JavaScript. I use the Crypto-JS library, but its performance is horrible. PBKDF2 is terribly slow, so I switched to another ...
6
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0answers
828 views

FIDO, U2F Compatibility

I've been following the FIDO standard (a consumer-friendly public-key system similar to SSH key pairs) and it appears that it's close to being complete: both Google and PayPal have been testing it ...
2
votes
1answer
87 views

What is the purpose of derivation of encryption and authorization keys from master key?

We're using AES-CBC and HMAC to encrypt and authenticate our messages (using encrypt-then-authenticate method). Sometimes I see solutions (like this one) which are deriving encryption and ...