Does anyone have, or have access to a simple API that can calculate the hashofthingtosign for old transactions along the blockchain? I'm just looking for something simple to see what the "Hashofthingtosign" is or was for transactions along the blockchain. One might even say this is a question of "how" do I do this, but it is well beyond me and is effectively a question of does anyone have one or know of one?

A simple API such as what is here; http://2coin.org/tx.asmx would be awesome (though I'm having a hard time accessing the website at this time). It was just a simple thing; you paste the transaction ID and it can spit out the R value, the S value, and the hashofthingtosign by reading probably the info from blockchain.info or something like that.

I'm trying to better understand the algorithm that's used, but it seems like block explorers don't keep track of that variable nor have implemented a simple detail of just showing what it was. I'm not asking for a huge program or something that would take someone weeks to do. The complexities of creating even a python script to look up this variable for old transactions and calculate it are well beyond my capabilities. Not to mention, without examples of the hashofthingtosign, how would I even be able to confirm whether I had done it correctly or not?

1 Answer 1


Try the page at https://2xoin.com/getRSZfromRawTX/

Paste a raw transaction into it, it will return the z values of each tx input.

The z value is the hash of the message that was signed.

It only works for bitcoin at the moment.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.