130 char long public key

[bit-wasp]

130 char long public key

[etienneroudeix]

Hi @afk11 thank you very much for your answer. All is clear now !

[afk11]

Hi

secp256k1 field elements are 32 bytes, so 64 bytes each in hex. However, the DER encoding of public keys includes an extra byte of prefix, indicating what form the key is.

there are 5 prefixes supported by bitcoin:
\x04 - an uncompressed key, (1 + 32 + 32 => 130 hex) prefix + x and y coordinate
\x02 + \x03 - compressed key, (1 + 32 => 66) prefix (including compression bit) and the x coordinate
\x06 + \x07 - hybrid compressed key, (1 + 32 => 66) prefix (including compression bit) and the x coordinate

The first three are commonly used in bitcoin. There may be protocols which omit the prefix because a specification dictates the full x+y point must be sent. But for this library, it is correct to include the prefix.