1. Playfair Cipher encoder

Text : ABCD efghi
Alphabet25 : abcdefghiklmnopqrstuvwxyz
Padding Character : x

Solution:

Alphabet = abcdefghiklmnopqrstuvwxyz

	1	2	3	4	5
1	a	b	c	d	e
2	f	g	h	i	k
3	l	m	n	o	p
4	q	r	s	t	u
5	v	w	x	y	z

Plaintext = abcdefghi
Split into pairs of letters (digraphs)
Pairs : ab cd ef gh i

Pad at end, if necessary
If one letter is left at the end, then pad to make it pair
Pairs : ab cd ef gh ix

Encryption :
ab = a(1,1), b(1,2) `=>` b(1,2), c(1,3) = bc, Letters on the same row (Replace each letter with the one to its right)

cd = c(1,3), d(1,4) `=>` d(1,4), e(1,5) = de, Letters on the same row (Replace each letter with the one to its right)

ef = e(1,5), f(2,1) `=>` a(1,1), k(2,5) = ak, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

gh = g(2,2), h(2,3) `=>` h(2,3), i(2,4) = hi, Letters on the same row (Replace each letter with the one to its right)

ix = i(2,4), x(5,3) `=>` h(2,3), y(5,4) = hy, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

Plaintext	: abcdefghix
Ciphertext	: bcdeakhihy

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2. Playfair Cipher encoder

Text : hello world
Alphabet25 : abcdefghiklmnopqrstuvwxyz
Padding Character : x

Solution:

Alphabet = abcdefghiklmnopqrstuvwxyz

	1	2	3	4	5
1	a	b	c	d	e
2	f	g	h	i	k
3	l	m	n	o	p
4	q	r	s	t	u
5	v	w	x	y	z

Plaintext = helloworld
Split into pairs of letters (digraphs)
Pairs : he ll ow or ld

Pad duplicate-letters
If a pair has same letters, insert a padding letter between them, to avoid revealing doubled letters in the ciphertext
Pairs : he lx lo wo rl d

Pad at end, if necessary
If one letter is left at the end, then pad to make it pair
Pairs : he lx lo wo rl dx

Encryption :
he = h(2,3), e(1,5) `=>` k(2,5), c(1,3) = kc, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

lx = l(3,1), x(5,3) `=>` n(3,3), v(5,1) = nv, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

lo = l(3,1), o(3,4) `=>` m(3,2), p(3,5) = mp, Letters on the same row (Replace each letter with the one to its right)

wo = w(5,2), o(3,4) `=>` y(5,4), m(3,2) = ym, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

rl = r(4,2), l(3,1) `=>` q(4,1), m(3,2) = qm, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

dx = d(1,4), x(5,3) `=>` c(1,3), y(5,4) = cy, Rectangle rule (Replace each letter with the one in its row, but in the other letter's column)

Plaintext	: helxloworldx
Ciphertext	: kcnvmpymqmcy

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