Bouncycastle adds 20 bytes SHA1 hash after plain secret key instead of two bytes checksum

[vanitasvitae]

As pointed out here and discussed on the mailing list (link pending), bouncycastle seems to falsely export secret keys when exporting them without a password. In that case, BC 1.59 seems to append a SHA1 hash after the secret key, instead of just a 2 bytes checksum.

I suspect, that only key export without a password is affected.

[ghost]

Thanks for the report. Fixed by #349.