1. $encode is allowing multiple padding switches to be specified, and uses them in a hierarchy regardless of the order used.
2. $decode is ignoring the 'pnz' switches or the lack of a padding switch, and instead attempts to find all 4 padding types at the end of the decrypted string.
Depending on the padding switch used when encrypting the string, decryption can result in false positives which removes too many bytes. The default PKCS#5 padding or the 'p' padding cannot be confused with each other, but it's easy for 'z' and 'n' to have false positives, as shown by this example:
//bset -t &v 1 $chr(192) | echo -a original = $bvar(&v,1-) | noop $encode(&v,bmcz,key) $decode(&v,bmcz,key) | echo 4 -a decrypted = $bvar(&v,1-)
original = 195 128
decrypted = 195
As I understand padding behavior, decode should only search for the default PKCS#5 padding if none of the 'pnz' switches are used, and should only search for 1 of the 4 methods specified by the p|n|z|$null padding switch.
This should make valid syntax have the pnz switches be mutually exclusive for both encryption and decryption. Instead, $encode allows all 3 padding switches to be used, and uses them in this order:
A. $encode pads with 'z' method if 'z' switch is present, regardless if it's the 1st or last of several padding switches.
B. Otherwise, $encode pads with the 'n' method if 'z' switch is present, regardless if 'n' switch is used and if 'n' precedes or follows 'p'.
C. Otherwise, $encode pads with the 'p' method only if it's the only padding switch used.
D. Otherwise, $encode pads with the standard PKCS#5 padding only if no padding switch is used.
$encode and $decode should permit only 1 or zero of the 'pnz' switches to be used.
$decode should only remove the 1 of 4 padding methods defined by which of the 'pnz' padding switches is used or their lack of use. This means that, if a different padding method is specified during decryption than used during encryption, the decrypted message should retain the padding added by the default PKCS#5 method, or the spaces from the 'p' method, etc.