Let me see, ixcoin - first commit aug 16 2011, showwallet - authored jul 12 2011.
Have no idea why they used addrtype 138 it's their problem now.
I believe 7-th bit has been reserved for "private addresses".
By the way, showwallet is already in the master branch (0.5.99).
Actual code (base58.h):
void SetSecret(const CSecret& vchSecret)
{
SetData(fTestNet ? 239 : 128, &vchSecret[0], vchSecret.size());
}
There's no explicit 7-th bit anywhere though, so you may pick any byte you like.
With arithmetic overflow it would be chr((addrtype + 128) & 255) == 10.
well thanks, now it can dump the wallet without problem with SecretToASecret and reverse modified, but still can't process privkeys, insists saying "Bad private key".