throughout this time, wallis had been close to the parliamentarian party, perhaps as a result of his exposure to holbeach at felsted school. he rendered them great practical assistance in deciphering royalist dispatches. the quality of cryptography at that time was mixed; despite the individual successes of mathematicians such as françois viète, the principles underlying cipher design and analysis were very poorly understood. most ciphers were ad hoc methods relying on a secret algorithm, as opposed to systems based on a variable key. wallis realised that the latter were far more secure – even describing them as "unbreakable", though he was not confident enough in this assertion to encourage revealing cryptographic algorithms. he was also concerned about the use of ciphers by foreign powers, refusing, for example, gottfried leibniz's request of 1697 to teach hanoverian students about cryptography.