BUG #19335: the function encrypt does not work correct - ERROR: encrypt error: Key was too big

The following bug has been logged on the website:

Bug reference: 19335
Logged by: Marco Lebahn
Email address: marco(dot)lebahn(at)kfw(dot)de
PostgreSQL version: 16.11
Operating system: SUSE Linux Enterprise Server 15 SP7
Description:

Hello,

we patched our Systems from 16.10 and 14.19 to the new minor-level 16.11 and
14.20.

No problems with 16.10 and 14.19 while we using the function encrypt and
decrypt

psql (16.10)
Type "help" for help.

postgres=# SELECT encrypt('sdafgsdfgsdafgasdf', 'thelongkeyfoobar', 'bf');
encrypt
----------------------------------------------------
\x74a761b105fbc8f535f666e952e00018deb1349fbf27a87b
(1 row)

postgres=# SELECT
convert_from(decrypt('\x74a761b105fbc8f535f666e952e00018deb1349fbf27a87b',
'thelongkeyfoobar', 'bf'),'SQL_ASCII');
convert_from
--------------------
sdafgsdfgsdafgasdf
(1 row)

postgres=#

After patching the function throws errors

postgres=# SELECT encrypt('sdafgsdfgsdafgasdf', 'thelongkeyfoobar', 'bf');
ERROR: encrypt error: Cipher cannot be initialized
postgres=# SELECT
convert_from(decrypt('\x74a761b105fbc8f535f666e952e00018deb1349fbf27a87b',
'thelongkeyfoobar', 'bf'),'SQL_ASCII');
ERROR: decrypt error: Cipher cannot be initialized
postgres=#

or here an other error

with 16.10 - No trouble
psql (16.10)
Type "help" for help.

postgres=# SELECT encrypt('sdafgsdfgsdafgasdf', 'thelongkeyfoobar1234',
'bf');
encrypt
----------------------------------------------------
\x9e8f9e9319266c9722f5803684c29ab16ee98d100cbfe350
(1 row)

trouble with 16.11

psql (16.11)
Type "help" for help.

postgres=# SELECT encrypt('sdafgsdfgsdafgasdf', 'thelongkeyfoobar1234',
'bf');
ERROR: encrypt error: Key was too big
postgres=# SELECT
convert_from(decrypt('\x9e8f9e9319266c9722f5803684c29ab16ee98d100cbfe350',
'thelongkeyfoobar1234', 'bf'),'SQL_ASCII');
ERROR: decrypt error: Key was too big
postgres=#

Is this a bug?