Hello there, I’m trying to generate a checksum using :crypto.hash/2, I want to hash the first 8 characters only of my string and get the result as a decimal value. More precisely I’m trying to generate the checksum using SHA1, in Javascript it would be something like that parseInt(sha1(str).substr…

You can avoid the conversion to Hex: iex(1)> :crypto.hash(:sha, "Hi?\x1fHi.") |> binary_part(0, 4) |> :crypto.bytes_to_integer() 174888039 Or: iex(1)> <<int :: integer-size(32), _ :: binary>> = :crypto.hash(:sha, "Hi?\x1fHi.") iex(2)> int 174888039

Ok, what exactly you are trying to achieve. Give us an example input and example output of what you want, maybe then it will be easier to understand what you want.

I’m trying to generate a checksum for the first 8 characters of a string using SHA1, in Javascript it would be something like that parseInt(sha1(str).substr(0, 8), 16); for a string “Hi?Hi.” it should be 174888039. Note the character “\x1f” between ? and H.

Your main problem is thinking that 2fd4e1c67a2d28fced849ee1bb76e7391b93eb12 is SHA-1 output, it isn’t . Just check out what value does the crypto:hash/2 produce and work from there (hint, you can use pattern matching to generate integer from binary).

Hmmmm. As far as I understand (I might be wrong tho :smiley: ) from :crypto.hash/2 documentation this is the message digest of SHA-1. what am I missing?

The digest is return as a binary representation. iex(18)> :crypto.hash(:sha, "abc123") <<99, 103, 196, 141, 209, 147, 213, 110, 167, 176, 186, 173, 37, 177, 148, 85, 229, 41, 245, 238>> So this binary representation must be converted to the integer you want. You are trying to use Integer.parse(.…

[image] cmkarlsson: |> Base.encode(16) |> Integer.parse(16) it’s Base.encode16(). Thank you so much!

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aligredo April 28, 2020, 1:14am 7

it’s Base.encode16().
Thank you so much!