1 of 14

Cryptography

Crack the code

How do you tell a secret when everyone is listening?

2 of 14

Where do you need security?

3 of 14

Secure communication

4 of 14

Electronic payment

5 of 14

Authentication

6 of 14

Encryption

is one way of protecting our information explained above

7 of 14

Encryption

Decryption

Converting from real words to gobbledegoop

​

​

​

Converting from gobbledegoop to real words

​

​

​

Real words

(Plain text)

Gobbledegoop (Cipher text)

8 of 14

Cipher

A pair of algorithms that tell you how to encrypt and decrypt.

​

​

9 of 14

The key is key!

Ciphers usually depend on unique keys that are usually only know by the people communicating.

10 of 14

Caesar Cipher

One of the earliest ciphers

Value

Letter

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

Value

Letter

0

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

11 of 14

Breaking the Ceasar Cipher

12 of 14

Vigenere Cipher

One of the earliest ciphers

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

0

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

G

I

R

L

S

W

H

O

C

O

D

E

R

O

C

K

S

6

8

17

11

18

22

7

14

2

14

3

4

17

14

2

10

18

A

W

E

S

O

M

E

A

W

E

S

O

M

E

A

W

E

0

22

4

18

14

12

4

0

22

4

18

14

12

4

0

22

4

6

4

21

3

6

8

11

14

24

18

21

18

3

18

2

6

22

G

E

V

D

G

I

L

O

Y

S

V

S

D

S

C

G

W

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

13 of 14

Breaking the Vigenere Cipher

14 of 14

Cryptography Today

Challenge 1:

You have two different color cards. How can you prove to a person who cannot tell the difference between any colors that they are different?�

Challenge 2:

You have a box with a secret present that you want to send to a friend. The post office people in your town open everything unless it has a lock.

How can you send this package without anyone but your friend and you opening it up?