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

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1
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0answers
41 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
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1answer
85 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 ...
0
votes
0answers
20 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 ...
1
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0answers
35 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
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1answer
48 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 ...
1
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0answers
58 views

Is hashing the HMAC secret key a good idea?

I'm implementing a REST API and I've generated 128-bit random API keys which are used with HMAC-SHA1 for authorization. Should I hash the secret key on both the client and server before using it, ...
1
vote
3answers
43 views

Detect message tampering without shared key and without certificate authority

Is it possible to detect if a message has been tampered with, without using MAC (i.e. shared key) and without using a "trusted" third party (i.e. certificate authority)? I'm pretty sure it's not, but ...
2
votes
1answer
54 views

Avoiding Replay Attacks on Lightweight Channel

I'm in the process of building a network of small devices (ARM microcontrollers with something like nRF24L01 connectivity). The controllers will be receiving commands from a central system over these ...
2
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0answers
89 views

HMAC solution for a rest API

I'm trying to learn some things about REST apis and one of the topics that I'm having some trouble is security. I'm using angularjs for web interface ans slim framework for the php api. I've read ...
0
votes
1answer
82 views

Which is better in “DH-group14-sha1 with hmac-sha2-256” and “DH-group-exchange-sha256 with hmac-sha2-256” from performance and security perspective?

In our product (embedded system), so far we were using diffie-hellman-group1-sha1 with hmac-sha1. But due to security concern we are planning to use diffie-hellman-group14 for key exchange and ...
1
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0answers
127 views

Want to implement a really good authentication mechanism for REST API

I own a web application (single page application with Angular), that asks for some data through a set of REST APIs based on my server-side application (using Play Framework 2.2.1). So basically, I'm ...
3
votes
3answers
101 views

How to simply and efficiently generate different keys from one password?

I saw here that using the same key to encrypt and mac (in that order) a message could eventually be unsafe. What is the best way to generate two different keys from the same password (using a PBKDF ...
1
vote
1answer
132 views

SSO via HMAC and shared key. Can this be improved?

Given an authenticated user on A.com, we want to redirect the user to B.com so that she'll be immedaitely authenticated. The scheme I'm considering is very basic: A.com and B.com both share key S. ...
0
votes
2answers
112 views

Have I crossed my t's and dotted my lower-case j's? (or, implementing AES, please help get some eyes on my code)

So, I used the crypto module in node.js to implement a secure key generator and encrypt/decrypt functions. Knowing that security's best friend is a spotlight on the implementation, I want to throw it ...
2
votes
1answer
75 views

HMAC needed with SSL/AccessToken in place?

Is using an HMAC in web service messages overkill if you are already using SSL and Access Tokens? I’m thinking of further ways to secure a service, and HMAC message signing is one. But it comes with ...
1
vote
1answer
60 views

Is there an advantage to applying pbkdf2 to a key that's used to generate a MAC?

We need to generate tamper-resistant URLs to access a service, which are then shared with the end-user. The URLs don't contain any confidential data, but we need to ensure that they have not been ...
3
votes
1answer
148 views

using counter instead of salt for hashing

I'm developing own protocol for secure message exchanging. Each message contains the following fields: HMAC, time, salt, and message itself. HMAC is computed over all other fields using known secret ...
1
vote
1answer
171 views

What key to use in HMAC

I need to use HMAC on a certain message to guarantee integrity, but I cannot figure out what are the requirements for the key to be given as input to the hashing algorithm. In particular I have to ...
0
votes
1answer
61 views

What key needs to be used to compute HMAC?

I use AES-128bit to encrypt files and I want to compute a HMAC for each one of the encrypted files to ensure their integrity. Can I use directly the AES KEY to compute HMAC or should I used a derived ...
1
vote
1answer
357 views

How is the HMAC key exchanged?

Just wondering about this. Does it need a PKI to work?
2
votes
1answer
246 views

What extra protection is added to an REST API over HTTPS by the use of some kind of HMAC?

I'm designing a RESTFUL API that will always be used over HTTPS, what security advantages over the use of HTTP Basic Auth could be brought to my system by using such kind of message authentication ...
1
vote
2answers
812 views

Is this REST service authentication system secure?

I have to implement a token based authentication for a RESTful web service. This is the first time I'm implementing security features in a software, and this is what I have in mind for now : The ...
1
vote
0answers
111 views

Generating API keys within an OAuth2 session for non-web-browser clients

I am using Google's OAuth2 for authentication for a website which also has a RESTful API component. I would like to support connections from clients which are not within a web browser. Also, I'd ...
1
vote
1answer
4k views

Security for REST api (user/pass auth vs hmac vs oauth)

I have two servers (one on Hetzner (I am calling it H) and other in my office (calling it O) ). I need to run a basic CRUD web service on O and the only consumer of the service is H. Data on O is ...
2
votes
2answers
71 views

Which signing strategy?

I have a device which should lock and unlock something after receiving a signed server response. So in the best case a loop would lock like this: User locks device User wants to unlock device User ...
-5
votes
2answers
108 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 ...
2
votes
1answer
664 views

NIST test vectors for HMAC-SHA-256

I'm working on an implementation of HMAC-SHA-256 in classic ASP (legacy code). I currently have it working, and the resulting values are correct compared to some test cases I came up with along with ...
8
votes
1answer
562 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. ...
9
votes
3answers
569 views

API message verification without storing private key?

I'm in the process of implementing a public API for my web service. Security is a key concern as money is involved. It seems the current common practice for "authenticating" users in API requests is ...
5
votes
3answers
2k views

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 ...
6
votes
1answer
609 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 ...
4
votes
3answers
226 views

What SSL options should not be used?

What SSL options should be avoided, due to recently discovered weaknesses? This might include symmetric algorithms, or MAC functions.
3
votes
1answer
153 views

Does the HMAC of symmetric key revealed weakens the encryption?

If I reveal the HMAC of encryption key, does it weaken the secrurity of the payload ? e.g, I would construct following security packet cipher: bf_cbc IV: initialization vector to the cipher key-md5: ...
4
votes
2answers
276 views

Online banking proof of transaction for vertification in court

So, when i do an online payment transaction i "sign" my transaction with my digipass using some sort of a MAC (HMAC) with a shared key and some information that is unique for this transaction. But ...
4
votes
1answer
113 views

How do I build a secure signing mechanism on top of HMAC

Say we have a system with strong shared keys (not passphrases), and we're trying to sign messages sent by the server that will be visible to an attacker. E.g. storing session state in a signed cookie. ...
2
votes
1answer
615 views

Web service HMAC authentication/anti-replay

I am creating a web service, which handles various requests from web clients. The client and server share a big secret key S, and when one part wants to send data, it calculates the token as follows: ...
2
votes
1answer
219 views

HOTP with as HMAC hashing algoritme a hash from the SHA-2 family

I'm looking into using a OTP solution. HOTP is a OTP solution that is based on a HMAC with as hashing algorithm SHA-1. The standards defines it this way. But... SHA1 (as we know) has been a ...
1
vote
2answers
163 views

How to guarantee counter synchronisation between client and server for counter in hmac-based one time password implementation?

This is a clone of a question I posted on Stack Exchange. Thought I might catch the eye of some different people who could help here. We are trying to implement a hmac-based one time password ...
3
votes
3answers
981 views

HMAC What is secure manner to distribute shared secret between client and server?

I am looking at ways to secure http communication using HMAC. My understanding is that in this scenario the client and the server both know a secret. This means the secret must be first generated on ...
3
votes
3answers
213 views

How do I transfer the HMAC?

I have a file I'd like to encrypt with a symmetric key using AES-256 and then use an HMAC for integrity. So I don't "roll my own" scheme which I know is a big mistake, what are the standards for using ...
5
votes
1answer
109 views

Authentication by Signing or MAC?

I'm still new to security, so I'm sorry if this question doesn't make sense or if I'm completely off base with something. I've got some messages I want to encrypt (probably with AES-256-CBC) and send ...
3
votes
2answers
2k 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 ...
2
votes
1answer
175 views

Can a salted hash be an effective MAC?

An HMAC is basically a "keyed hash". Only the correct message and the correct key will produce a particular hash digest efficiently. Conceptually speaking, the same can be said for a salted hash; ...
4
votes
1answer
157 views

Is there a tree hash form of MAC that can be used when encrypting data for storage on S3 using multipart upload?

I am storing files on S3, some of which are very large, and need to be stored encrypted. I had planned on using Galois Counter Mode since it includes the MAC, however this won't work with multipart ...
1
vote
3answers
421 views

Validate hmac with hashed stored key

What if an HMAC is correctly generated and sent with the data to the server, so far I know the server needs to know the original data with which the MAC was created in order to re-create the MAC and ...
3
votes
2answers
244 views

Reusing HMAC state for multiple messages

I have a secret key k and message m. I send m || HMAC(m, k) to some other party, who can verify the integrity of m, assuming that they know k. Suppose I have multiple messages m1, m2, and so on. ...
10
votes
1answer
647 views

When authenticating ciphertexts, what should be HMACed?

Some have argued for using AES-256-CTR with HMAC-SHA-256 for authenticated encryption over AEAD-specific modes like EAX and GCM. However, when doing, this, what should be HMAC'd? And how? ...
2
votes
3answers
673 views

Proper hash_hmac key creation

I'm looking for, but unable to find, some definitive information on how long to make the secret and what characters are useable in creating a HMAC signature in PHP using SHA256. I found some ...
18
votes
3answers
10k views

How/When do i use HMAC?

I was reading HMAC on wikipedia and i was confused at 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 ...
4
votes
1answer
352 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 ...