Questions tagged [sha-256]

SHA-256 is part of the SHA-2 family of hash functions with a 256-bit output and a 128-bit security level.

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Is this a secure (and correct) sign-then-encrypt technique for transferring messages?

After reading some information on the way iMessage works I have been working on writing some code to try my hand at securely transferring messages in a similar manner and I wanted to confirm that the ...
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796 views

Is it safer to use timestamp in REST authentication?

I am working on a personal project to build a REST authentication system which authenticate clients via three parameters: ...
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35 views

Does fixing partial bits of a SHA256 hash increase the probability of finding a preimage using the meet-in-the-middle attack?

Let’s say I want to find a partial rather than full preimage using the meet-in-the-middle attack. For example, my goal is to find a preimage so that the first 76-bit output of the hash are all ...
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95 views

Idea behind internal SHA-2 functions

In the SHA-2 family, specifically SHA-256, there are functions called Sigma0 and Sigma1, which look like this: ...
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76 views

Can I prove that hash of modified preimage is valid

Assume that hash(X) == Y Alice knows both X and Y Bob only knows Y Alice generates a random nonce N and shares it with Bob. Alice calculates H = hash(X⊕N) and shares H with Bob. Can Alice prove to ...
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KCV scheme that encrypts a hash over key and IV

Is there anything wrong with this key-check value scheme? This question is a follow-up to an earlier question of mine. In summary, I want to devise a key-check value scheme that will enable my ...
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256 views

Handling key invalidation

I'm writing an Android app which will need to store some data for the user as a byte array of unknown length. The data must be encrypted. I have gone down the path of the hardware-backed keystore and ...
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60 views

Hash function notations and their corresponding existing cryptographic hash algorithm

I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions $...
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60 views

Keys and key-stretching when authenticating requests?

I'm making a REST application and still a bit confused about this issue. basically, to authenticate incoming requests, I give out userId, issued timestamp, expiry timestamp (normally 3 months after ...
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123 views

Designing an AES-based protocol for controlling and acessing ioT boards via RF

I'm designing an open ioT protocol to be used on ioT boards based on Texas Instruments RF-based MCUs. These MCUs have an AES module to easily encrypt and decrypt AES content, so that's why I choose a ...
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1answer
40 views

Pre-Image Resistance of repeated, patterned SHA2-256 digests

Suppose $H = \operatorname{SHA2-256}$. Let $H_1 = H(\text{“Alpha1”})$. Let $H_2 = H(\text{“Alpha2”})$. … Let $H_N = H(\text{“AlphaN”})$. So all these digests are based off a common pre-image post-...
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Why initialize values and array SHA256 with specific buffer?

Why initialize values and array SHA256 with specific buffer? ...
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Rotate values in predefined manner

I want to create a Server S1, that publish a different value every 10 minutes on the internet. The value looks something like f7826da6-4fa2-4e98-8024-bc5b71e0893e. ...