Code that helped end Apartheid

Traditionally, encode meant to use one word/symbol to represent another, while encipher meant to transform one (usually mathematically) into another.

For example, "Tora, Tora, Tora" was a code that had no intrinsic meaning, but was the signal to proceed with the Pearl Harbor attack. No way to reverse that.

Meanwhile, "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG" can be transformed with a Caesar cipher to "QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD". It can easily be reversed.