Alice and Bob are two spies that are under disguise in a hostile territory. They need to be in contact with each other regularly and share information about their mission.
computer science
Description
Decoding a Secret Message
Alice and Bob are two spies that are under disguise in a hostile territory. They need to be in contact with each other regularly and share information about their mission. They cannot risk compromising their communication, so they decided to use encryption. Alice and Bob both have two alphabet lists, the first one is the alphabet they use for sending their messages and the second one is a dummy alphabet to make it harder to decode their messages. The main alphabet is L and the dummy alphabet is L2:
The letters from L are mapped to letters in L2. So {a} is mapped to {m}, {b} to {n}, {c} to {o}, and
{d} to {p}. They send information using letters from L, but they also add letters from L2 to increase
the complexity of encryption. Based on their communication rules, when either of them sends a
message, it must contain words that have letters from L and L2. There are some twists:
1. The meaningful words in any message they broadcast are words that are “completely mapped”. All the other words are meaningless.
2. Since L2 is mapped to L, they can use both set of letters interchangeably: so a string like “abnm” is indeed completely mapped since “n” is mapped to “b” and “m” is mapped to “a”.
3. Once you find the mapped words, you have to remove all letters from L2 to find the actual
message (which is all in L)
