Cryptographers in various countries began experimenting with long, unstructured cryptographic keys (random keys—a long sequence of random numbers spanning hundreds of sheets of paper) and with one-time pad cyphers, cryptographic keys that were destroyed after use and never used again. In some ways, this was a holy grail for cryptographers, as it was an absolutely secure system. Indeed, if it were possible to test all possible keys, the true message would be revealed, along with several false positives. However, one-time pad cyphers were almost never used, due to their impracticality on the battlefield and in general, due to the enormous quantity of papers that had to be delivered somehow, without risking them falling into enemy hands. A curious fact, however, is that in some cases, where communications are rare and cost is irrelevant, the one-time pad cypher is still used: this is the hotline between the American and Russian (formerly Soviet) governments.
