# Problem of the Week Problem A Dated Messages

A Caesar Cipher is a way to create secret messages by shifting letters in text. For example, a Caesar Cipher of $$3$$ shifts each letter in the text by $$3$$. If you want to shift the letter D by $$3$$, then you count three letters forward to arrive at the letter G. Similarly, if you want to shift the letter E by $$3$$, then you count three letters forward to arrive at the letter H. So in a Caesar Cipher of $$3$$, the letter D is encoded with the letter G, the letter E is encoded with the letter H, and so on. When shifting letters, if you reach the end of the alphabet, you continue counting at the letter A. For example, if you want to shift the letter Y by $$3$$, then you count forward to Z, then to A, and end up at the letter B.

1. Using a Caesar Cipher of $$3$$, encode the message FRACTIONS.

2. To decode a secret message you shift the letters in the opposite direction. For example, in a Caesar Cipher of $$4$$ the letter G would be decoded as C.
Decode the message AEXIVPSS using a Caesar Cipher of $$4$$.

3. A Date Cipher shifts the letters in a message by the corresponding digit of a date in the form YYYYMMDD. If the message is longer than the date, then we repeat the date as many times as necessary. In the table below, the message FRACTIONS has been encoded using the digits from the International Womenâ€™s Day, $$20240308$$.

Original Letter F R A C T I O N S
Digit of Date $$2$$ $$0$$ $$2$$ $$4$$ $$0$$ $$3$$ $$0$$ $$8$$ $$2$$
Encoded Letter H R C G T L O V U

The secret message for FRACTIONS would be HRCGTLOVU.

A famous mathematician has the birthdate December $$9$$, $$1906$$ ($$19061209$$). Use the Date Cipher and this date to decode the message HAAIFJOYQNR to find the name of the famous mathematician.

Theme: Computational Thinking