Affine Cipher (encoder / decoder) Examples

1. Affine Cipher encoder

Text : ABCD efghi
Slope (A) : 3
Intercept (B) : 5
Alphabet : abcdefghijklmnopqrstuvwxyz

Solution:

The Affine cipher is a cipher, where each letter of plaintext is mapped to its numeric equivalent and then encrypted using a linear function y=(ax+b) mod m and then converted back to a letter.

Alphabet = abcdefghijklmnopqrstuvwxyz

Plaintext	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z
x	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25
(3x + 5)	5	8	11	14	17	20	23	26	29	32	35	38	41	44	47	50	53	56	59	62	65	68	71	74	77	80
(3x + 5) mod 26	5	8	11	14	17	20	23	0	3	6	9	12	15	18	21	24	1	4	7	10	13	16	19	22	25	2
Ciphertext	f	i	l	o	r	u	x	a	d	g	j	m	p	s	v	y	b	e	h	k	n	q	t	w	z	c

Plaintext	: ABCD efghi
Slope (a)	: 3
Intercept (b)	: 5
Ciphertext	: FILO ruxad

2. Affine Cipher encoder

Text : hello world
Slope (A) : 3
Intercept (B) : 5
Alphabet : abcdefghijklmnopqrstuvwxyz

Solution:

The Affine cipher is a cipher, where each letter of plaintext is mapped to its numeric equivalent and then encrypted using a linear function y=(ax+b) mod m and then converted back to a letter.

Alphabet = abcdefghijklmnopqrstuvwxyz

Plaintext	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z
x	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25
(3x + 5)	5	8	11	14	17	20	23	26	29	32	35	38	41	44	47	50	53	56	59	62	65	68	71	74	77	80
(3x + 5) mod 26	5	8	11	14	17	20	23	0	3	6	9	12	15	18	21	24	1	4	7	10	13	16	19	22	25	2
Ciphertext	f	i	l	o	r	u	x	a	d	g	j	m	p	s	v	y	b	e	h	k	n	q	t	w	z	c

Plaintext	: hello world
Slope (a)	: 3
Intercept (b)	: 5
Ciphertext	: armmv tvemo

This material is intended as a summary. Use your textbook for detail explanation.
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1. Examples