SHA1 Hash Values - Technical Question
 

I was working on some educational research and I noticed that SHA1 values are normally comprised of Hex characters. Yet many of the file hash values seen on P2P consist of all alphabetical characters and 2-7. I did some research (including this board) and understand there is a difference between SHA1 methods (Base 16 -vs- Base 32) can someone please:

1) Explain the difference in the two SHA1 calculations (is it just a BASE issue? Am I using the correct terminology?)

2) Explain how to generate the P2P like hash of a file (sha1sum in linux only gives Hex)

3) MOST IMPORTANT - can you convert between Base16 and Base32 (assuming I am using correct terminology) WITHOUT the original file, can a BASE32 hash be generated from the Base16 hash value alone and not recalculated from original file? If so how?

:bangh:

Thank you, yes I have seen that Wikipedia article and it is very interesting, unfortunately, as far as i could see (or understand), there is no discussion of the "Base" output of the message digest. This is what I am most interested in. I get the feeling it is probably much easier than I am making it, unfortunately I'm just not getting it and am looking for some expert teachings!...


To clarify my original post, I'll paraphrase from another old post I was reading on another forum and someone asked a similar question and I am still looking to understand it. Why when a .gif file's SHA1 message digest is generated it can result in these different outputs:

SHA1 - DZ2UNZISKKGDLT4TBXCYZWVBL3NAMCM7 (Base32)
SHA1 - 3161bf6ac6c9c49df0eba30d7db7d1e5713e7a76 (file as Text)
SHA1 - 1e7546e512528c35cf930dc58cdaa15eda06099f (file as Binary)

Are these 3 outputs related? Can I convert the Base32 into one of the others WITHOUT the original file?

I'll leave the research up to you as that is what I'm guessing you are getting a grade on and should be doing the work on...

but...seems to me if you 'reverse engineer' a base 32 value back to its source then resolve it to a binary/text it would work...of course that's just theory...such things are rather not my cup of tea considering I completed college 25 years ago....anyway, while I can do a fair amount of upper level math I'm confident that hacking hash values is beyond me

http://www.webmaster-talk.com/php-fo...md5-value.html

considering Hash values are supposed to be secure, its a rather hard process to decrypt them, but possible