𝐂𝐨𝐝𝐞𝐬 𝐚𝐧𝐝 𝐂𝐢𝐩𝐡𝐞𝐫𝐬

𝐀𝐟𝐟𝐢𝐧𝐞 𝐂𝐢𝐩𝐡𝐞𝐫

Type: Substitution
(Note: it's formula for encryption is f(x)=(ax+b)mod n, and for decryption is f(y)=a^-1(y-b)mod n, where "a" should be coprime of "n", "x" or "y" corresponds on the position of the letter in the alphabet (see rotation code), and "b" is any value of input, and mod n is the limit of rotation)
Example: (encryption)
Plaintext: AFFINE
a=5, b=8, n=26
F(x)=(ax+b)mod26
A=0, F(0)=(5(0)+8)mod26=8
F=5, F(5)=(5(5)+8)mod26=33
F=5, F(5)=(5(5)+8)mod26=33
I =8, F(8)=(5(8)+8)mod26=48
N=13, F(13)=(5(13)+8)mod26=73
E=4, F(4)=(5(4)+8)mod26=28
A=08=I
F=33=H
F=33=H
I =48=W
N=73=V
E=28=C
Ciphertext: IHHWVC
Example: (decryption)
Ciphertext: IHHWVC
a=5, b=8, n=26
F(y)=a^-1(y-b)mod n
I =08, f(8)=5^-1(8-8)mod26=0
H=33, f(33)=5^-1(33-8)mod26=5
H=33, f(33)=5^-1(33-8)mod26=5
W=48, f(48)=5^-1(48-8)mod26=8
V=73, f(73)=5^-1(73-8)mod26=13
C=28, f(28)=5^-1(28-8)mod26=4
I =0=A
H=5=F
H=5=F
W=8=I
V=13=N
C=5=E
Plaintext: AFFINE

~~~CTTRO