Below is a list of pairs, which are related to one another. Select the pair of items, which represent the integral reliance on the first item to enforce the second?
1) The separation of duties principle, the 'least privilege' principle
2) The parity check, the limit check
3) The single-key system, the Rivest-Shamir-Adelman (RSA) algorithm
4) The two-key system, the Data Encryption Standard (DES) algorithm