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Questions tagged [hmac]

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

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Why are HMAC signatures frequently used for webhook authorization but not other HTTP API requests?

HMAC signatures are very commonly used for webhook authorization from service to consumer. Examples: Stripe Slack Twilio Twitter GitHub and hundreds and hundreds more. This seems a near universal ...
Paul Draper's user avatar
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1 vote
2 answers
131 views

Why does TLS use two separate sequence numbers?

In TLS separate implicit sequence numbers for sent and received packets are used to calculate the HMAC in the record layer. The RFC 5246 says: Each connection state contains a sequence number, which ...
PCFX's user avatar
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2 votes
1 answer
977 views

CSRF: Signed Double Submit Cookie & 'Referer' validation vs MITM and vulnerable subdomains

I have been researching various techniques for preventing CSRF attacks, such as SOP, SameSite, Secure, Referer validation, and CSRF Tokens, and their potential bypasses. During my research, I ...
Advena's user avatar
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1 answer
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Session based CSRF Tokens - What value do i use with JWT?

The Double Submit Cookie CSRF Token pattern is a stateless technique that doesn't require storage or a database. However, it's vulnerable to session hijacking attacks and sub-/sibling domains that are ...
Advena's user avatar
  • 129
1 vote
1 answer
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javascript: how to apply block cipher to byte stream

I am writing browser javascript that has a pre-shared key with nonce, and creates a binary websocket connection. How can I apply block encryption-authentication such as AES-GCM to the messages? Is it ...
personal_cloud's user avatar
2 votes
1 answer
163 views

I using sha256 after adding a secret enough if the message includes its length?

I've been reading about HMAC protecting from length extension attacks, but if the message already specifies it size, is HMAC adding any advantange to simple hashing after prepending a secret? As ...
6502's user avatar
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2 votes
0 answers
136 views

What would be the most complete procedure to get a simple login system working securely?

I don't have formal CS education but i've written one or 2 little websites. I have troubles communicating even in my native language but i hope this is understandable. With simple i mean something ...
Silly_Code_Valley's user avatar
0 votes
1 answer
481 views

Key derivation for HMAC, concatenate vs multiple HMAC passes

I'm trying to build a generic function to encrypt HMAC values with a single global secret key, but that can be "scoped" or salted by application/uses. For instance, an HMAC for a session ...
Cristiano Coelho's user avatar
0 votes
1 answer
339 views

Is an HMAC of an email address with a permanent secret key a good way to generate security tokens for unsubscribing from an email list?

I'm writing a mailing list manager program. For subscribing and unsubscribing, I'm considering using HMACs of email addresses with secret keys to generate unsubscribe links. This key would be ...
Someone's user avatar
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0 votes
1 answer
272 views

Is is safe to pass an API key in a HMAC hash?

I have 2 websites: a.com and b.com To avoid using SAML for Single-Sign-On and making things complicated, I've taken this approach: a.com is the identity provider. All users will be asked to sign in on ...
Zach's user avatar
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1 vote
1 answer
485 views

What exactly happens when you use 2FA with "Password" + "Yubikey HMAC" Login in KeepassXC?

Usecase: KeepassXC is configured with a Passward + Yubikey HMAC. I am trying to understand the exact steps that happen. I think the first five Steps are clear: Open KeepassXC Enter Password Select ...
foshyboy's user avatar
1 vote
0 answers
522 views

How exactly does OpenVPN's tls-auth option apply HMAC to packet messages?

Update: I've been able to work out everything I was asking about packet structure when I was finally able to get Wireshark to work, but there is one last thing I'm confused on which I detail at the ...
Letal1s's user avatar
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0 votes
1 answer
215 views

How does HMAC fit in BLE?

In BLE there is events like authentication, pairing, bonding, exchange of LTK to secure a link, etc... How does HMAC fit in BLE? I know that HMAC is used to ensure the integrity of a message so does ...
Belphegor's user avatar
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0 answers
328 views

Why we need complicate truncation for the OTP?

If we assume that Time based OTP generates the OTP using the hash function like SHA-3. Then, the generated OTP would Hash(Secret, Shared time). We want a shortened string rather than a full hash ...
Curious_man's user avatar
1 vote
1 answer
2k views

HMAC SHA256 by using a static key + text as a key

Maybe it's not a good idea, but I would like to check it with you. When using HMAC SHA to hash a clear text value (string max 30 char) I need to use a key (256) but in my scenario this key is static ...
Marc Alves's user avatar
0 votes
2 answers
608 views

Digital signature for API authentication feasible?

Could it be practical to authenticate API request through digital signature (based on headers and message body)? This would be asymmetric instead of something like HMAC which is not a signature. ...
jhurtas's user avatar
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2 votes
2 answers
242 views

Am I authenticating devices securely?

I'm building a IOT platform for my home as a hobby. Currently, I'm trying to implement device authentication. A device in my case could be a Raspberry Pi, Arduino, Jetson Nano. To authenticate devices ...
Riki's user avatar
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0 answers
100 views

Usage of HMACs to verify the licensing during production

We have a production that uses our software (put on a chip) and a requirement that we need to limit the amount of chips produced for each customer (so they need to buy a license) - so they can't ...
Archeg's user avatar
  • 101
0 votes
1 answer
546 views

How does TLS use hashing from the negotiated cipher suite

I am trying to understand why TLS only uses hashing algorithm like SHA-384 instead of using an HMAC instance like HMAC-SHA-384. If I understand correctly, this cipher suite (...
A.Ho's user avatar
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2 votes
2 answers
229 views

Benefits of HMAC-based server authentication

Context and assumptions: TLS 1.2 or 1.3, server authentication only Client uses HMAC to authenticate itself to the server, using a PSK key Client is a library, not a web browser, which doesn't allow ...
user avatar
0 votes
1 answer
940 views

HTTP authentication with client-side private key

I'm designing a web service meant for storing data for users, but these users don't have proper server-side accounts, just a random master key the user generated and stores on their device (a bip39 ...
Rafael Korbas's user avatar
1 vote
0 answers
830 views

HMAC hashing vs JWTs for stateless authentication

For simple authentication with backend services, without more sophisticated needs (e.g. roles and scopes), is there any security benefit in using JWTs instead of sending HMAC hashes to verify a ...
David Min's user avatar
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0 votes
2 answers
348 views

Is it feasible to calculate an HMAC-SHA512/256 MAC from an environment that only supports HMAC-SHA512?

I need to verify a MAC for something signed with HMAC-SHA512/256, however, the language I'm using (Salesforce's Apex language) doesn't have support for that algorithm. It does have HMAC-SHA512 and ...
Synchro's user avatar
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2 answers
422 views

Keyed Hash Function (HMAC) For Unguessable URLs?

I have numeric IDs that I would like to use in filenames. So for example with IDs 1, 2, 3 we would have 1.jpg, 2.jpg, and 3.jpg Now the problem is that clearly a user could just guess 4.jpg and view ...
Zout's user avatar
  • 103
0 votes
1 answer
242 views

Combining confidentiality, authenticity and data integrity to form secure URL

There are clients (mobile application), they can share links to their profile info, which should be confidential. The link expires in 5 minutes (configured). They set Auth-Code so that the one who ...
mshwf's user avatar
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2 votes
3 answers
1k views

Is a simple random+hmac session cookie breakable?

I make session cookies of form session_id+'|'+hmac_sha256(session_id, static_secret) where session_id = random_string(16 bytes) made with a PRNG (not a CSPRNG!) seeded on the server's timestamp at ...
capr's user avatar
  • 123
0 votes
2 answers
162 views

Does using subkeys provide better protection in this instance?

I was thinking of implementing the following scheme for encryption of many independent files: From the password, which is given by the user, generate a master key using for example HMAC-SHA. From ...
HerpDerpington's user avatar
0 votes
0 answers
607 views

Best secure approach with Basic Auth

Due to several customer reasons our product needs to support Basic Auth as primary authentication mechanism with client's service account. We are using Bcrypt to store customer's password in our DB, ...
Kucera.Jan.CZ's user avatar
1 vote
1 answer
2k views

REST API is protected by HMAC based authentication. What does including URL path in the message protect from?

I have came across a REST API for some commercial software, that checks authentication by requiring HMAC on concatenation of http_method (GET, PUT, etc) timestamp payload (body of a POST / PUT ...
Andrew Savinykh's user avatar
1 vote
0 answers
1k views

How to uses FIDO2 hmac-secret extension for offline authentication? [closed]

How hmac-secret extension defined in the CTAP2 Specification is used to help implement offline authentication with an authenticator. Is there any other specification that says how to do this? From the ...
Dinesh Kumar Sarangapani's user avatar
1 vote
1 answer
835 views

Use the public key of a certificate as the key for HMAC SHA

Consider the following scenario. A company has several computers for each users on the same domain. They purchase an RSA certificate from a recognized authority which will be deployed with private / ...
Marc Alves's user avatar
1 vote
1 answer
148 views

Need a test vector for the putty ssh-2 file mac validation

I'm trying to implement the putty file format in one of my dart packages. Implementing the actual key loading was ok, but I'm struggeling with the mac validation. I'm not shure what I'm doing wrong ...
Richard Burkhardt's user avatar
2 votes
1 answer
160 views

Using encryption key as input keying material

Libsodium supports Blake2 for key derivation. It seems like you shouldn't truncate the output to get two keys (eg one encryption/one mac) as the recommended way is to use a counter as the salt for ...
Guest's user avatar
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0 answers
25 views

Does TLS provide data integrity? [duplicate]

I've looked around on this site and I've not seen a clear answer on this question. From what I've read TLS does not provide data integrity unless specific ciphers are used which use HMAC'ing as part ...
user1876202's user avatar
1 vote
1 answer
361 views

Is md5(data + key) secure if a proper hmac function isn't available?

I need to generate a MAC signature for data on a website, but it's in a HTML templating system where there's only a few functions available. The only hashing function available is md5. Ideally, I'd ...
David Chanin's user avatar
1 vote
0 answers
156 views

HMAC with random application Id and secret with DPAPI

We have open endpoints because there is a flow where access token is still not presented. Because of that, I've implemented HMAC + DPAPI (using Azure Blob Storage) to store the keys, without involving ...
Expressingx's user avatar
2 votes
1 answer
5k views

Which one to use AES : GCM vs CBC

I am planning to encrypt database fields using AES encryption. Now, this encrypted data will not transfer over the internet and will reside in our own datacenter only. From what I read, GCM mode ...
Ankit Bansal's user avatar
1 vote
2 answers
143 views

Terminology question - authentication through encryption

I came across a number of somewhat similar solutions, which are based on the knowledge factor related to a symmetric key in particular: If a party was able to generate correct message authentication ...
user avatar
3 votes
1 answer
978 views

Why HMAC/Signed API requests are not prevalent compared to API keys or JWT based requests

While all/majority of AWS APIs requests are signed with HMAC, it is not as prevalent for other APIs in general. Most likely, the reason is because of the gotchas involved when client has to make the ...
Jyosna Security's user avatar
0 votes
0 answers
106 views

What is the need of HMAC in Diffie-Hellman? [duplicate]

When Alice and Bob both have the same shared secret to encrypt their data (Diffie-Hellman) and Alice encrypts her data with this key and Bob can decrypt it with the same key, then Bob knows that the ...
Lars Laf's user avatar
0 votes
0 answers
962 views

cracking HMAC-SHA1 when the password and seed are inverted

I happen to have a few hashes generated with code that did this (it has been changed to use a more "standard" bcrypt call): $ python3 >>> import hmac >>> hmac.new(b'The ...
mathieu's user avatar
  • 125
4 votes
1 answer
330 views

Can I HMAC my plaintext for use as a NACL SecretBox nonce?

I'm writing an application that needs to deterministically encrypt some data (where two equal ciphertexts will produce two equal plaintexts; this is acceptable and in fact desirable for this ...
fe_alice's user avatar
0 votes
0 answers
529 views

Is it safe to use HMAC to create an API key?

I am planning to create an API key using the user's password as message and a random number assigned to that user in my database as key (or vice-versa). I will then store the hash of that API key in ...
ThunderSea's user avatar
0 votes
1 answer
2k views

Is HMAC-SHA256 more secure to hide information than SHA256?

I need to save user email on a public database but I don't want to do it in plaintext, so I need to hash it. If somebody wants to verify if some email exists in the public database, he or she can ...
Halloween1977's user avatar
-1 votes
1 answer
203 views

How authenticate a login with javascript

I want to authenticate a user using a username and password in a web app running javascript interfacing to a non node js or php server. In a normal desktop app I could use bcrypt or an hmac or ??. ...
kidzopa's user avatar
0 votes
1 answer
431 views

Is HMAC really a benefit for AES-CBC?

I think I quite well understand the theoretical benefit of adding the HMAC (authenticity/integrity on top of confidentiality), but I am looking at this from a key management point-of-view. Premise: ...
smoothware's user avatar
2 votes
1 answer
193 views

How does Algolia's virtual API keys work?

Algolia allows you to generate virtual/secured API keys from another parent API key but without a call to their servers. A virtual key thus generated on the server side with a defined "scope" (like ...
jeffreyveon's user avatar
0 votes
1 answer
161 views

What advantage does HMAC provide in generating short hashes comparing to regular hash function?

This question is specific to the Apple/Google Contact Tracing framework. See https://www.blog.google/documents/56/Contact_Tracing_-_Cryptography_Specification.pdf for the cryptography spec. In this ...
yegle's user avatar
  • 101
0 votes
1 answer
932 views

How to use Yubikey 5 NFC for online accounts, Linux login, and KeePassXC?

I just got my Yubikey 5 NFC, and would like to use it for Linux desktop login Linux KeePassXC (which only supports hmac-sha1 challenge-response) online accounts When reading about U2F it seams to be ...
Sandra Schlichting's user avatar
1 vote
2 answers
380 views

Can I use PBKDF2 derivation function to generate a MAC in PKCS12 file?

It seems that the default password based key derivation function that is used by PKCS12 to generate a MAC is this one. It is unique to the standard and probably not used anywhere else. Is it possible ...
username's user avatar
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