4

As I know, standard ECDSA digital signature algorithm returns two values (according to this article or Wikipedia), but transaction push services or APIs, like this one, require one string as a signature. Can anyone explain, what is that string, and how can I get it with those values? Is it possible with OpenSSL? Thank you very much!

1 Answer 1

3

The ECDSA digital signature scheme returns two values. To be specific, the X and Y values computed on the elliptic curve are returned.

In Bitcoin the signture is DER encoded, which is represented as a string containing the X and Y values and also some header data. But both X and Y can easily be extracted from it when reading the string from left to right.

In fact the Bitcoin protocol uses more information than only those concerning the X and Y values. For example, the size of the DER encoded signature is specified, but also a so called signature type is used to define which part of the transaction the signature was computed for.

Take a look here under the section "Signing the transaction" to see exactly how it works. In the table you will see how a computed signature is used in a scriptSig.

The details regarding the DER encoding was discussed here.

Your Answer

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

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