Topic: How do you decompress a public key? (Read 2514 times)
I don't believe that you can derive the uncompressed public key from just the compressed public key. I'm pretty sure that you need the private key for that.
A compressed public key contains 02 or 03 at the fist byte, followed by 256-bits of the X.
https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm
How do you calculate the Y, out of it?
I see that the client just calls EC_KEY_set_conv_form with POINT_CONVERSION_COMPRESSED, but since I need to do it in an app which not use OpenSSL, could anyone please refer me to some doc/code explaining the math behind this process?
https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm
How do you calculate the Y, out of it?
I see that the client just calls EC_KEY_set_conv_form with POINT_CONVERSION_COMPRESSED, but since I need to do it in an app which not use OpenSSL, could anyone please refer me to some doc/code explaining the math behind this process?
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