Strong cipher algorithms are cryptographic systems resistant to cryptanalysis, they
are not vulnerable to well-known attacks like brute force attacks for example.
A general recommendation is to only use cipher algorithms intensively tested and promoted by the cryptographic community.
More specifically for block cipher, it's not recommended to use algorithm with a block size inferior than 128 bits.
Noncompliant Code Example
PLS_INTEGER := DBMS_CRYPTO.ENCRYPT_DES
PLS_INTEGER := DBMS_CRYPTO.ENCRYPT_AES256