Questions tagged [hmac]
HMAC is a method for constructing a message authentication code based on a cryptographic hash function.
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Mixed HMAC / GMAC with fixed IV [duplicate]
I was just thinking about improving the performance of HMAC - what would be the issues in doing the following:
Let $G_K(IV,M)$ be GMAC with a key $K$, for IV and message $M$.
Let $H$ be a secure hash ...
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1answer
45 views
How does AWS Secret key and access key work
Those keys are too short to be public/private RSA keys. What are they? How does it use them to authenticate the client?
My guess is:
AWS access key ID is a form of unique user/account identifier
AWS ...
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1answer
50 views
AES-GCM cipher tag and IV size, while attempting to render encrypted ciphertext useless by removing them
I'm using AES in GCM mode of operation for encryption/decryption & authentication of segments of data in a file. The layout of each segment can be summerized by this diagram. Each segment is ...
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2answers
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Would a HMAC digest make sense in an RSA / ECDSA signature?
When MD5 and SHA1 were broken there was, each time, a scramble to upgrade software and certificates to remove the offending algorithm. However, in each case, the HMAC variant of each hash function was ...
2
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1answer
50 views
HMAC computation using AES key
I want to compute an HMAC value of a data set using CKM_SHA256_HMAC mechanism with AES key. I have the error code CKR_KEY_TYPE_INCONSISTENT because it seems that I need to use a key of key_type ...
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1answer
79 views
Hash for use in embedded HMAC application
I developed a GNSS logger (http://flysight.ca) which has become popular for scoring skydiving competitions. At the moment, there is little protection against competitors falsifying tracks, but I would ...
2
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1answer
54 views
Authenticated encryption and file data integrity
I've got a task to provide the integrity and an authenticated encryption for files in our application. I need an assurance if my way of thinking is correct.
I can't use AES GCM, I have to stay with ...
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Is reverse engineering SHA256-HMAC function possible? [duplicate]
Assume HMAC function is used to generate a 6-digt integers time-based onetime password. As follows:
$$K_h =\operatorname{HMAC}(k,t) = H((k\oplus\text{opad})\mathbin\| H((k\oplus\text{ipad})\mathbin\|...
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Orignal Krawczyk's HKDF vs latest NIST SP800-56C
I've noticed that the original HKDF in rfc5869 defines a feedback loop. So the pseudo-code is something like:
...
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1answer
145 views
Worth taking performance hit of HMAC to gain additional security?
It seems like SHA-512 truncated to 256 bits is usable as a MAC [1]. The advantage is that it's ~50% faster than HMAC-SHA-256 on 64-bit CPUs and ~50% faster than HMAC-SHA-512 on short inputs. (My use ...
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1answer
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Which is more secure? $\operatorname{AES-ECB}(key,\operatorname{SHA1}(data+key))$ vs $\operatorname{HMAC-SHA1}(key, data)$ [closed]
$\operatorname{AES-ECB}(key,\operatorname{SHA1}(data+key))$ vs $\operatorname{HMAC-SHA1}(key, data)$
Which is more secure?
Which is faster?
There is a similar comparison here; HMAC-SHA1(key, data) ...
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2answers
177 views
GMAC vs HMAC in message forgery and bandwidth
Saarinen in his work GCM, GHASH and Weak Keys says that;
The GHASH algorithm belongs to a widely studied class of Wegman-Carter
polynomial universal hashes. The security bounds known (this and ...
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0answers
29 views
Is there an instance where integrity protecting metadata is bad?
In JWEs there's a unprotected data field as well as recipients are not integrity protected. Is there a case where integrity protecting this data would be a problem? If it doesn't make a difference, ...
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1answer
105 views
Finding the Input if Hash Value, Hash Function, and Key are known
Let's assume that we have a hash value $h$ is calculated by using HMAC-SHA256.
We have the key $k$. We also know some information about the input:
It contains a pattern like 15 numbers where first ...
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1answer
158 views
How does the user get the private/public key with HMAC based request signing?
I need to implement a HMAC signing of requests and I have read this article which explains the basics of what it is and how to achieve on theory.
https://blog.andrewhoang.me/how-api-request-signing-...
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1answer
79 views
What are the different use cases between an HMAC and digital signature? [duplicate]
I understand that both an HMAC and digital signature are used to check the integrity and authenticity of a message. Further, I understand that a digital signature is non-repudiatible.
What I do not ...
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1answer
334 views
Do I understand HMAC-SHA-xxx and HMAC-SHA-xxx-yyy correctly?
I've recently started looking at HMAC, and there a few things that I'm not 100% sure that I'm understanding correctly. Am I right about these three things?
HMAC-SHA-xxx has an output length of xxx ...
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What lightweight cryptographic hash function for short input could I use for HMAC?
I am looking for a cryptographic hash function that I can configure for HMAC. The input that I will hash is around 50 bytes. The function must be fast, and computationally lightweight.
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1answer
28 views
Correlate HMAC key and MAC without message
If I have a HMAC_SHA1 MAC and a potential key, can I check whether this key could have produced this signature without knowing any of the message body plaintext?
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3answers
102 views
AES-GCM not using two keys
It is recommended to use different keys for different purposes, such as encryption and integrity protection. As I see it, AES-GCM only requires one key as input. Two different keys are then generated ...
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1answer
192 views
HMAC-SHA-512 with a 256-bit key
I am implementing hmac-sha-512 in an integrated system. However, one subsystem is only supports the use of 256-bit keys.
I read in https://tools.ietf.org/html/rfc4868 that:
However, note that [...
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3answers
252 views
Encrypt-then-MAC with base64
I've a doubt about the Encrypt-then-MAC approach when using HMAC-SHA256 with AES128 in CBC mode, as seen in https://en.wikipedia.org/wiki/Authenticated_encryption.
I need to encode the resulting ...
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1answer
292 views
HMAC-SHA512 output randomness?
This is regarding an online roulette game that claims to be fair. Here is the explanation:
Two strings are created:
...
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1answer
45 views
Cryptographically secure hash function vulnerable to length extension attacks both to front and to back?
Is there any hash function where both $\text{hash}(m\|k)$ and $\text{hash}(k\|m)$ are vulnerable to length extension, but $\text{hash}(m)$ is itself secure?
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2answers
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Could a 6502 CPU safely compute a SHA-1 hash in a reasonable length of time?
The 6502 is the CPU in a Tamagotchi (which can be hacked to run custom code). SHA-1 is the default hash used for TOTP (the algorithm used by two-factor authentication tokens and apps). Hopefully you ...
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2answers
54 views
How to provide partial confidentiality and full integrity for a protocol message?
I want to provide confidentiality and integrity for a protocol. I don't want to encrypt the entire protocol message. I do not want to encrypt the header and timestamp of the protocol message, but I ...
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3answers
922 views
When do I need to use CBC and HMAC?
As I know CBC does not provide integrity for the message, thus HMAC is used to provide integrity for CBC message. Also, I hear about CBC-MAC which can provide integrity and confidentiality. Which one ...
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2answers
195 views
Security difference between $\mathrm{Keccak}(k\mathbin\|x)$ and $\mathrm{Keccak}(x\mathbin\|k)$
$\require{begingroup}\begingroup
\DeclareMathOperator{\keccak}{\mathrm{Keccak}}
\DeclareMathOperator{\concat}{\|}
$According to Keccak's website, $\keccak(k \concat x)$ is safe:
Unlike SHA-1 and ...
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0answers
233 views
Is it still safe to use sha1 as an hmac hash function in 2018 [duplicate]
I'm curious if it's safe to use sha1 for an HMAC in 2018 in a platform product.
A popular vendor (Twilio) uses an HMAC with sha1 with a shared secret to validate that messages they send are indeed ...
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2answers
217 views
Is an AEAD the recommended method to add encryption + HMAC to a protocol?
Assuming you are dealing with a competent developer/team, and you are advising on adding security to their protocol. Also for the time being lets not worry about the key establishment and validating ...
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1answer
102 views
Authentication scheme using HMAC
I have an authentication service, a client and an application service.
The client needs to use the application, but they have to be authenticated first. I'm trying to create a simple scheme to do ...
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1answer
83 views
Challenging Question for the Build a Secure MAC with Special Properties
We would like to ask you to give a construction for requested scheme which provides those properties or give a proof that is not achievable.
[Note that unsuccessful attempts to build such a scheme ...
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3answers
136 views
Two salts, One password
If I have two different MD5 password hashes with two different salts (the salts are known), is there any way to cryptographically deduce if the two passwords match? Other than brute force password ...
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1answer
232 views
What is the reason of using Pedersen Commitment scheme over HMAC?
I want to implement non-interactive Bit Commitment scheme for messages of arbitrary length.
And I am curious, what is the reason of using Pedersen Commitment scheme over Salted Hash (in other words ...
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1answer
1k views
HMAC Key Sizes for MD5, SHA1, SHA224|256|384|512
I'm trying to find an authoritative source for the HMAC Key sizes for each of the hashing algorithms below. Specifically for TLS implementations of HMAC.
I found this table in RFC5246:
...
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2answers
255 views
HMAC does it matter if I chose the cipher text or the plain text as the message? [duplicate]
I am using HMAC to create a message authentication code. My question is, does it matter if I use cipher text + encryption key or ...
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0answers
50 views
Is this a more effective HMAC? [duplicate]
I was given an argument in a conversation today and I don't know how to respond to it:
H( k || m || k ) should be a better choice of MAC than the traditional HMAC. The person's rationale was that: "...
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1answer
49 views
Signing different types of messages with the same asymmetric key
I want to be able to sign different types of messages with the same asymmetric key. (For completeness, I am using Ed25519 for my signatures).
Why do I want to do this?
The same key is used to sign ...
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1answer
304 views
HMAC SHA256 for deriving session keys using random nonce
I need to derive session key in order to create an application layer secure channel between mobile app and a bluetooth device. My scheme is similar to
this scheme that uses a HMAC and counter.
...
2
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1answer
210 views
Is transporting a salt, IV, ciphertext and HMAC in an encrypted token an acceptable practice?
I’m porting over some crypto code from Mcrypt (deprecated) to OpenSSL. I’m following a process that a former employee implemented, which is as follows:
Create a random salt for use in a PBKDF2 key ...
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2answers
2k views
How many trials does it take to break HMAC-MD5?
I know that you can find collision in MD5 with 2^64 trials using Birthday paradox. Now everyone is saying that HMAC-MD5 is significantly more secure. How can I ...
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2answers
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What is a size of mac_length and mac_key_length for TLS cipher suites HMAC using SHA384 and SHA512?
i failed to find explicit definition of hash output size and mac_key_size for hmac based on SHA384 and SHA512.
RFC5246 specifies:
but defines only
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0answers
154 views
How to implement security - authenticity/confidentiality/integrity for 6/14 bits radio messages?
I just took over two radio systems (using 433Mhz) - one communicates with 6 bit messages, one with 14 bit messages. Both have a lots of transmitters and one receiver (and, yes bits not bytes).
For ...
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2answers
108 views
Is HMAC a suitable substitute for HKDF?
My PHP version does not include the hash_hkdf() function, and upgrading versions is not worth the trouble for my project (which is for personal pleasure, not for ...
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1answer
107 views
6 Byte for HMAC in wireless system secure?
A wireless system has 8 byte payload and 6 byte for message authentication.
Scheme:
...
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1answer
98 views
Which one is better using DSA, or MAC and encryption?
I want to authenticate server messages to clients. The communication between clients and server is unicast. As I know I can use either used MAC or DSA.
by using MAC, I required a shared key between ...
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0answers
57 views
Tree structure with XTS and HMAC: MAC in parent
Situation:
A file format contains a tree-like data structure; parent nodes can find children and child nodes can also find their (single) parent. To protect confidentiality, the nodes in the file are ...
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1answer
375 views
MAC size 128 bits or more?
Just a quick question:
I've seen implemented BouncyCastle's class AeadParameters with MAC length of 128 bits, which was allegedly recommended.
Though when I looked up HMac to implement my own MAC in ...
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1answer
35 views
Expanding truly random key into printable password for successive hashing
The STUN network protocol defines its client authorization in the terms of message-integrity check employing the following scheme [RFC5389, section 10.2]:
$$
\DeclareMathOperator{\HMAC}{HMAC}
\...
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1answer
324 views
Recommended key lengths for BLAKE2b
RFC 7693 provides the following table of standard parameter sets for BLAKE2b without a key (where nn is the hash size in bytes):
...
