SGT

1

UJHANTAMAWMUZVGKTERRYKUB BPGXMKYMBBPYXMOGOEHDEFGH

Assume we have a plaintext, such as THE, compare with first ciphertext UJH.

Won't come up in exam.

2

THE BEST ROTOR MACHINE WAS DEVELOPED BY ARTHUR [SURNAME]

3

atneginuigheimartna

4

skipped

5

3	5	7	1	4	2	6
T	h	e	E	n	i	g
m	a	c	i	p	h	e
r	m	a	c	h	i	n
e	h	a	d	t	h	e
c	o	n	f	i	d	e
n	c	e	o	f	G	e
r	m	a	n	f	o	r
c	e	s	w	h	o	d
e	p	e	n	d	e	d
o	n	i	t	s	s	e
c	u	r	i	t	y	z

EICDFONWNSIIHIHDGOOESYTMRECNRCEOCNPHTIFFHDSTHAMHOCMEPNUGENEEERDDEZECAANEASEIR

6

A: Trying to equate left side of current round to next round of right side. B: Wrong round function. C: Correct structure. D: Key is wrong. E: Correct structure.

7

LD_{16 - i} || RD_{16 - i} &= RD_{i} || LE_{i} \\ LD_{13} || RD_{13} &= RE_3 || LE_3 \\ \\ \text{Encryption side:} \\ LE_4 &= RE_3 \\ RE_4 &= LE_3 \oplus F(RE_3, K_4) \\ \\ \text{Decryption side:} \\ LD_{13} &= RD_{12} = LE_{4} = RE_{3} \\ RD_{13} &= LD_{12} \oplus F(RD_{12}, K_4) \\ &= RE_{4} \oplus F(LE_{4}, K_4) \\ &= RE_{4} \oplus F(RE_{3}, K_4) \\ &= (LE_3 \oplus \cancel{F(RE_{3}, K_4)}) \oplus \cancel{F(RE_{3}, K_4)} \\ &= LE_3 \end{aligned}$$ ## 8

\begin{aligned} RD_0 &= LE_5 \ &= RE_4 \ &= LE_3 \oplus F(RE_3, K_4) \ &= RE_2 \oplus RE_3 \oplus K_4 \

\end{aligned}