Bitcoin Forum

https://docs.google.com/spreadsheets/d/1mOTrqckdetCoRxY5QkVcyQ7Z0gcYIH-Dc0tu7t9f7tw now works.  It computes the SHA-256 hash of the null string or a string of up to 55 printable ASCII characters.  It does so from scratch, so to speak; it calculates the 2 set of constants.  All steps are fully revealed demonstrating the intricate details of the algorithm.

Ken Shirriff was my inspiration.  http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html

Nice!

Where you inspired by this?
http://gizmodo.com/mining-bitcoin-with-pencil-and-paper-1640353309 (http://gizmodo.com/mining-bitcoin-with-pencil-and-paper-1640353309)

Yes, but I've gone considerably further now.

donations to 17MCh7jJ4dHU5iAfLPv2t8hdjGDDzn95DK

I'm thinking about my next enhancement.  Any suggestions/requests?

There was a thread [1] where someone asked about generating a BTC address by hand. Basic idea would be to start with a number as private key and go from there.


[1] found it https://bitcointalk.org/index.php?topic=816123.0

Is there a way to type in a string to hash and get the SHA256 of it? I would like to compare to results to something like http://www.xorbin.com/tools/sha256-hash-calculator.

Copy the sheet (File->Make a copy...) (it is now standalone, i.e. it no longer uses any script) and then in your copy go to 'input'!B2 and enter up to 55 printable ASCII characters.  The resulting 512-bit hash will be displayed as 64 hex-digits at 'post-round 64'!A10.

I used that same site to double check the results of;

{the null string} (leave the cell empty)
e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

abc
ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad

,.<>;':"/?[]\{}|`~!@#$%^&*()_-+=
55ef293e848487fb2673965531ef1777332307044b178f44fa970f63ed251125

I am content.

I am willing; I will research it.

Oh dear; per https://en.bitcoin.it/wiki/Technical_background_of_Bitcoin_addresses, it requires the SHA256 hash of 65 bytes.  As it stands as of now my sheet only handles up to 55 printable ASCII characters.  I will need to enhance it to handle one more chunk (medium effort) and binary/hex input (easy).

Far worse; the very first step involves "Having a private ECDSA key" which looks to be crazy hard to do in a sheet.

You will also need RIPEMD-160, BASE58Check and be able to get a public ECDSA key from a private one. All sounds complicated on paper.


From what I read [1] its "just" a number between 0x0 and 0xFFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140 which would be given as input by you.

[1] https://en.bitcoin.it/wiki/Private_key

Well, ok, yes, the very first step is not too tough but per http://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm it gets hard fast.

Since you are using Excel maybe this VB.net code may help you:
http://www.reddit.com/r/Bitcoin/comments/1utg95/how_do_you_calculate_a_public_key_from_the/celjnof (http://www.reddit.com/r/Bitcoin/comments/1utg95/how_do_you_calculate_a_public_key_from_the/celjnof)
Although you'll need ecPoint object which may not be available through Excel.

If you want to roll your own EC calculations good starting points are here:
http://arstechnica.com/security/2013/10/a-relatively-easy-to-understand-primer-on-elliptic-curve-cryptography/ (http://arstechnica.com/security/2013/10/a-relatively-easy-to-understand-primer-on-elliptic-curve-cryptography/)
http://procbits.com/2013/08/27/generating-a-bitcoin-address-with-javascript (http://procbits.com/2013/08/27/generating-a-bitcoin-address-with-javascript)

It could be done, there are some already written attempts in Python, but I can tell you it's some work. IMHO it's best to enhance your table to accept longer strings, and leave Eliptic curve cryptography out of the Excel.

Although I started off in Excel at the very beginning, I am now working in Google sheet.  I found the Google sheet script engine to be *very* slow.

Thank you for the pointers but EC looks a little tougher than I am willing to take on at the moment.

I am working on my SHA256 Google sheet to get it to handle longer strings, i.e. 119 (as opposed to just 55), right now; tedious.  I am wondering when I might trip over some limitation, e.g. number of tabs, etc., in Google sheet.

I've added some "instructions" within the sheet.  Enjoy.