First Principles AI

Solution

Use the mapping $A=1,\dots,Z=26$ .

Word: CLASS

C=3,\ L=12,\ A=1,\ S=19,\ S=19

Encryption key (addition):

k=-3+4i

\begin{aligned} C:&\ 3+(-3+4i)=4i\\ L:&\ 12+(-3+4i)=9+4i\\ A:&\ 1+(-3+4i)=-2+4i\\ S:&\ 19+(-3+4i)=16+4i\\ S:&\ 19+(-3+4i)=16+4i \end{aligned}

Encrypted values:

(4i,\ 9+4i,\ -2+4i,\ 16+4i,\ 16+4i)

\begin{aligned} 4i-(-3+4i)&=3\\ (9+4i)-(-3+4i)&=12\\ (-2+4i)-(-3+4i)&=1\\ (16+4i)-(-3+4i)&=19\\ (16+4i)-(-3+4i)&=19 \end{aligned}

So the decrypted word is CLASS.

\boxed{\text{Encrypted: }(4i,9+4i,-2+4i,16+4i,16+4i)\ \to\ \text{Decrypted: CLASS}}