Evento se você usar o mesmo comando em diferentes ocasiões, você terá saídas diferentes. A razão é que toda vez que uma nova chave AES-256 é gerada e protegida com sua senha.
openssl aes-256-cbc -e -a -in password.txt
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
U2FsdGVkX19yNQwed5/Sq3b6/3UFGGOGVD1dSA7aCZI=
openssl aes-256-cbc -e -a -in password.txt
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
U2FsdGVkX19rulpZRi8u5K9iJKVN5FVFRb6ngFY1BWM=
openssl aes-256-cbc -e -a -in password.txt
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
U2FsdGVkX192MxevxHvc1wW0dh9P4HctQF/75HEPVB4=
openssl enc -aes-256-cbc -k test -P
salt=667E42EDE61BEA35
key=46FB1D91FC400A8E26A8B0E38CF505F026263299CF0FA541217FBC6CEED1FC0B
iv =10A3858EC9D718AB91FC45B98786FDCC
openssl enc -aes-256-cbc -k test -P
salt=34F9B481E391A831
key=CDF1D936F99147BB56B4E3441B5E1A68A15838FE43F234AA7EB9A9F903B0BD61
iv =A649443D096E6976420F4941C2608CC8
openssl enc -aes-256-cbc -k test -P
salt=51AC4B4388D5C25B
key=D70AF8238D1C597F074123C9BB23B76C9CA04AAF2C986C4A56F96CB0FF1365F9
iv =D70FB991EEE776FCD45A67830CBD3202