# Cryptology Handout ```McKenzie Andreatta
Nathan Ducey
Angelo Marchesini
Reilly Roach
Cryptography Goodies
VOCAB
Cryptography: the study of the techniques of writing and decoding messages.
Plaintext Matrix: The original message once it has been put into numerical and matrix
form.
Cipher Matrix: the matrix that will allow us to encrypt the message. Also, the cipher matrix
must be a square invertible matrix.
Encrypting: the process of putting a message into secret code. For us this means
multiplying the plaintext matrix by the cipher matrix.
Ciphertext Matrix: The result of multiplying the cipher matrix by the plaintext matrix.
Decrypting: the process of making the message intelligible again by using the inverse of
the cipher matrix and multiplying it by the ciphertext matrix.
Steps of Encrypting and Decrypting
Encrypting:
1. Choose a nxn matrix to be the cipher matrix and call it A.
2. Write out your message and assemble vectors with n entries. Then, using the
vectors as columns, you get a matrix and we will call this P.
3. Assign each letter a number and apply to your matrix (A=1, B=2, etc.)
4. To encrypt, we then multiply AP=C, where C is the ciphertext matrix.
Decrypting:
1. Identify the ciphertext matrix.
2. Then determine A-1 (The inverse of the cipher matrix).
3. Multiply A-1C=D, where D is the decrypted matrix.
4. Convert the entries of your decrypted matrix back to text to identify the
secret message!
A
1
B
2
C
3
D
4
E
5
F
6
G
7
H
8
I
9
J
10
K
11
L
12
M
13
N
14
O
15
P
16
Q
17
R
18
S
19
T
20
U
21
V
22
W
23
X
24
Y
25
Z
26
_
27
```