Implement HMAC From Scratch

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Your question is Implement HMAC From Scratch. Start with the requirements on the right.

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Problem

Implement HMAC from scratch in your preferred language.

Implement hmac_sha256(key, message), treating both inputs as UTF-8 strings and returning the lowercase hexadecimal HMAC-SHA256 digest. Use a 64-byte SHA-256 block size, hash keys longer than one block, and apply the standard inner and outer padding constants.

Constraints

0 <= len(key) <= 10^5 characters
0 <= len(message) <= 10^6 characters
Inputs contain valid Unicode strings
Use SHA-256 as the underlying hash
Return exactly 64 lowercase hexadecimal characters

Function Signature

def hmac_sha256(key, message):

Your solutionPython 3

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