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Calculating a SHA hash with a string + secret key in python

Asked 2009-08-20T14:23:36.187
59

Amazon Product API now requires a signature with every request which I'm trying to generate ushing Python.

The step I get hung up on is this one:

"Calculate an RFC 2104-compliant HMAC with the SHA256 hash algorithm using the string above with our "dummy" Secret Access Key: 1234567890. For more information about this step, see documentation and code samples for your programming language."

Given a string and a secret key (in this case 1234567890) how do I calculate this hash using Python?

----------- UPDATE -------------

The first solution using HMAC.new looks correct however I'm getting a different result than they are.

http://docs.amazonwebservices.com/AWSECommerceService/latest/DG/index.html?rest-signature.html

According to Amazon's example when you hash the secret key 1234567890 and the following string

GET
webservices.amazon.com
/onca/xml
AWSAccessKeyId=00000000000000000000&ItemId=0679722769&Operation=I
temLookup&ResponseGroup=ItemAttributes%2COffers%2CImages%2CReview
s&Service=AWSECommerceService&Timestamp=2009-01-01T12%3A00%3A00Z&
Version=2009-01-06

You should get the following signature: 'Nace+U3Az4OhN7tISqgs1vdLBHBEijWcBeCqL5xN9xg='

I am getting this: '411a59403c9f58b4a434c9c6a14ef6e363acc1d1bb2c6faf9adc30e20898c83b'

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1 Answer

20
import hmac
import hashlib
import base64

digest = hmac.new(secret, msg=thing_to_hash, digestmod=hashlib.sha256).digest()
signature = base64.b64encode(digest).decode()

I know this sounds silly, but make sure you don't have a trailing space on your secret by accident.

answered 2012-08-28T19:13:36.353

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