From: Brian Candler <b.candler@...>
Date: 2009-08-12T19:52:50+09:00
Subject: Re: sha1/base64

ben ******* wrote:
> i try to compute the SHA-1 : sha = Digest::SHA1.hexdigest(input)
> I obtain correct result => 9A2115CC03E05F99A996FBCE47C4554905D75D1D
> 
> After this first operation, i try to obtain the same result in Base64
> (res=Base64.b64encode(sha)). If the operation was created with success,
> i should obtain => miEVzAPgX5mplvvOR8RVSQXXXR0=
> But, i find an other result and i don't understand what is the meaning
> of that ?

Since you didn't show what you *actually* get from your base64 encoding, 
it's hard to be sure what you're doing wrong. But I guess you are base64 
encoding the output of 'hexdigest' which is a hex string (40 ASCII 
characters 0-9 and A-F) rather than the 20 bytes binary.

Compare:

>> "miEVzAPgX5mplvvOR8RVSQXXXR0=".unpack("m")
=> ["\232!\025\314\003\340_\231\251\226\373\316G\304UI\005\327]\035"]
>> "miEVzAPgX5mplvvOR8RVSQXXXR0=".unpack("m").first.size
=> 20

versus:

>> str = ["9A2115CC03E05F99A996FBCE47C4554905D75D1D"].pack("m")
=> "OUEyMTE1Q0MwM0UwNUY5OUE5OTZGQkNFNDdDNDU1NDkwNUQ3NUQxRA==\n"
>> str.unpack("m")
=> ["9A2115CC03E05F99A996FBCE47C4554905D75D1D"]
>> str.unpack("m").first.size
=> 40

If you want to generate the former, then use Digest::SHA1.digest() 
instead of Digest::SHA1.hexdigest()

>> require 'digest/sha1'
=> true
>> Digest::SHA1.digest("hello")
=> "\252\364\306\035\334\305\350\242\332\276\336\017;H,\331\256\251CM"
>> Digest::SHA1.hexdigest("hello")
=> "aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d"
>> 
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