On Tue, May 29, 2018 at 5:13 AM, Jonas Schnelli via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

Hi

If 520 bits are present, first 256 bits are the BIP32 chain code, to second 264
bits (33 bytes) define the public key (according to BIP32)

In a 33 byte compressed public key, only 1 bit from the first byte conveys information. The other 7 bits can be discarded. This will allow you to reduce the bech32 encoded result by one character.