CRYPTOGRAPHY | Encrypting & Decrypting | Caesar Cipher | Modulo Operator | TAGALOG-ENGLISH

Summary

This video delves into cryptography, focusing on encrypting and decrypting messages using Caesar cipher and modulo operator. It explains the roots of 'cryptography' and its role in creating secret codes. The Caesar cipher shifts letters by a set number, either to the left or right, for encryption and decryption. The modulo operator uses a key to encrypt by adding it to letter positions and then taking modulo 26 to wrap around the alphabet. The video provides step-by-step examples of both encryption and decryption processes, illustrating how to convert plain text into coded messages and vice versa.

Takeaways

• 🔐 Cryptography is the practice of secure communication, involving the use of codes to encrypt and decrypt messages.
• 📜 The term 'cryptography' comes from 'crypto' meaning hidden and 'graphene' meaning writing, indicating its purpose of hidden writing or secret messages.
• 🔄 Encryption is the process of transforming plain text into code using an algorithm, while decryption is the reverse process.
• 🔄 Caesar Cipher is a type of shift cipher where each letter in the plaintext is shifted a certain number of places down the alphabet.
• 🔢 The modulo operator is used in cryptography to encrypt and decrypt messages by adding or subtracting a key to each letter's position in the alphabet.
• 🔑 A key in cryptography is a crucial piece of information used to encrypt or decrypt a message, often shared between the sender and receiver.
• 🔄 For Caesar Cipher, the direction of shifting can be to the left or right, and decryption involves shifting in the opposite direction.
• 🔄 When using the modulo operator, if the result of the encryption exceeds the alphabet size, it wraps around using the modulo operation.
• 🔢 The modulo operator in encryption is represented as ( c = (p * k) % 26 ), where c is the encrypted letter, p is the original letter's position, k is the key, and 26 is the number of letters in the alphabet.
• 🔄 Decryption using the modulo operator involves reversing the encryption process by subtracting the key from the encrypted letter's position and applying the modulo operation.

Q & A

What does the word 'cryptography' mean?

The word 'cryptography' originates from the two Greek words 'crypto', which means hidden, and 'graphene', which means writing. Therefore, the meaning of cryptography is hidden writing or the practice of creating and breaking secret codes.

What are the two main processes in cryptography?

The two main processes in cryptography are encryption and decryption. Encryption is the process of transforming plain text into code form using a certain algorithm, while decryption is the process of converting the coded message back into plain text.

What is a key in the context of cryptography?

In cryptography, a key is a string of information that is used to reveal the encrypted message into a readable form.

What is the Caesar Cipher method?

The Caesar Cipher method is a type of shift cipher where each letter in the plain text is shifted a certain number of places down or up the alphabet. The key in this method is the number of positions each letter is shifted.

How does the Caesar Cipher method work for encryption?

In the Caesar Cipher method for encryption, each letter of the plain text is shifted to the right by a certain number of positions determined by the key. For example, with a key of 3, 'A' becomes 'D', 'B' becomes 'E', and so on.

How is decryption performed in the Caesar Cipher method?

Decryption in the Caesar Cipher method is performed by shifting the encrypted letters in the opposite direction of the encryption. If the encryption used a shift to the right, decryption shifts to the left by the same number of positions.

What is the role of the modulo operator in cryptography?

The modulo operator in cryptography is used to encrypt and decrypt messages by adding or subtracting a key to the numerical position of each letter in the alphabet and then finding the remainder when divided by 26 (the number of letters in the alphabet).

How does the modulo operator help in encrypting a message?

When encrypting a message using the modulo operator, each letter of the plain text is converted to its corresponding numerical position, a key is added to it, and then the result is taken modulo 26 to ensure it falls within the range of the alphabet. The resulting number is then converted back to a letter.

Can you provide an example of how the modulo operator is used for decryption?

For decryption using the modulo operator, each numerical position of the encrypted letter is reduced by the key and then taken modulo 26. For example, if 'E' (which is 4) is encrypted with a key of 3 to become 'H' (which is 7), decryption would involve 7 - 3 mod 26, resulting in 4, which corresponds back to 'E'.

What happens if the result of the modulo operation goes beyond the alphabet range during encryption?

If the result of the modulo operation goes beyond the alphabet range during encryption, it wraps around to the beginning of the alphabet. For instance, if the result is 27, it would be taken as 1 (since 27 mod 26 is 1), which corresponds to 'A'.

How does the Caesar Cipher differ from using the modulo operator for encryption?

The Caesar Cipher is a specific type of shift cipher with a fixed number of positions for shifting letters, while the modulo operator can use any integer value as a key, providing a wider range of possible encryptions. The modulo operator also ensures that the result always stays within the bounds of the alphabet.

Outlines

00:00

🔐 Introduction to Cryptography

The script begins by introducing the topic of cryptography, which is defined as the practice of secure communication in the presence of third parties. The term 'cryptography' is derived from 'crypto' meaning hidden and 'graphene' meaning writing, thus implying the concept of secret or hidden messages. The video discusses two primary processes within cryptography: encryption, which is the transformation of plain text into coded form using an algorithm, and decryption, which is the reverse process of converting coded messages back into plain text. Two methods of cryptography are highlighted: the Caesar cipher, a type of shift cipher, and the use of the modulo operator. The script also explains the concept of a key in cryptography, which is a piece of information that helps reveal the encrypted message in a readable form.

05:39

🔄 Caesar Cipher Method

This paragraph delves into the Caesar cipher method, a type of substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet. The script provides an example of encryption using a shift of three to the right, demonstrating how the word 'cryptography' is encrypted to 'swwuhqiruw'. It then explains decryption as the opposite process, using a shift of five to the left to decrypt the cipher back to the original word. The script emphasizes the importance of understanding the direction of shift for both encryption and decryption.

10:40

🔢 Modulo Operator in Cryptography

The script moves on to discuss the use of the modulo operator in cryptography. It explains that the modulo operator is used with a key to encrypt messages, and this key can be any integer value from 0 to 25. The script provides an example of encrypting the message 'mmw is fun' using a key of five, where each letter's position in the alphabet is increased by five and then reduced modulo 26 (the number of letters in the alphabet) to ensure the result is within the alphabet range. The result of this encryption is 'rrb nxkz'.

15:40

🔄 Decrypting with Modulo

This paragraph explains the decryption process using the modulo operator. The script uses the encrypted message 'rrb nxkz' and the key of five to decrypt it back to 'mmw is fun'. It shows how each letter's position is decreased by the key value and then reduced modulo 26 to find the original letter. The script also provides another example of encryption and decryption using the modulo operator with different messages and keys.

20:45

🔚 Conclusion on Cryptography

The final paragraph wraps up the discussion on cryptography, summarizing the key points covered in the video. It reiterates the importance of the Caesar cipher and the modulo operator in encrypting and decrypting messages. The script concludes by emphasizing the practical applications of these cryptographic methods in secure communication.

Keywords

💡Cryptography

Cryptography is the practice and study of secure communication in the presence of third parties called adversaries. Derived from 'crypto' meaning hidden and 'graphene' meaning writing, it refers to the process of making information secret. In the video, cryptography is discussed as the method of encrypting and decrypting messages to ensure secure communication. It is the central theme of the video, with examples of encryption and decryption being provided.

💡Encryption

Encryption is the process of encoding a message or information in such a way that only authorized parties can access it. It involves the transformation of plaintext into ciphertext using an algorithm. The video explains encryption as a method to convert readable text into an unreadable form, ensuring that the message remains secret. The Caesar cipher and modulo operator are two methods discussed for encryption.

💡Decryption

Decryption is the reverse process of encryption, where the encoded message is converted back into its original form. The video mentions decryption as the counterpart to encryption, where the hidden message is revealed back into plain text. It is essential for the recipient to understand the secret message sent by the sender.

💡Caesar Cipher

The Caesar Cipher is a type of substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet. In the video, the Caesar Cipher is used as an example of a simple encryption method where a key (shift value) is used to shift the letters of the message to the right to encrypt and to the left to decrypt.

💡Modulo Operator

The modulo operator is used in mathematics to find the remainder of a division of two numbers. In the context of the video, it is applied in cryptography to encrypt messages by adding a key to the numerical position of each letter in the plaintext and then taking the remainder when divided by 26 (the number of letters in the alphabet). This method is used to demonstrate a more complex form of encryption than the Caesar Cipher.

💡Key

In cryptography, a key is a piece of information (such as a password, phrase, or a series of numbers) that determines the output of the encryption or decryption process. The video explains that the key is crucial for both encryption and decryption and must be shared between the sender and the receiver to ensure the message can be understood.

💡Plaintext

Plaintext refers to the original, human-readable form of a message before it has been encrypted. The video uses the term to describe the starting point of the encryption process, where the message is in a form that can be easily understood before being transformed into ciphertext.

💡Ciphertext

Ciphertext is the result of an encrypted message, which is transformed from plaintext using an encryption algorithm. In the video, ciphertext is the unreadable form of the message that is produced after applying the Caesar Cipher or modulo operator to the plaintext.

💡Shift

In the context of the Caesar Cipher, a shift refers to the number of positions each letter in the plaintext is moved to encrypt or decrypt the message. The video provides examples of using a shift of three to the right for encryption and a shift to the left for decryption.

💡Alphabet

The alphabet, in the context of the video, refers to the set of letters used in a language, specifically the English alphabet which contains 26 letters. It is the basis for the Caesar Cipher and modulo operator methods, where each letter is assigned a numerical position to facilitate encryption and decryption.

Highlights

Cryptography is defined as the practice and study of hiding and revealing information.

The word 'cryptography' comes from 'crypto' meaning hidden and 'graphene' meaning writing.

Cryptography involves two processes: encryption and decryption.

Encryption is the process of transforming plain text into code using an algorithm.

Decryption is the process of converting an encrypted message back into plain text.

Shift cipher or Caesar cipher is a method in cryptography.

The modulo operator is another method used in cryptography.

A key in cryptography is essential for revealing encrypted messages.

The Caesar cipher involves shifting letters in the alphabet by a certain number.

Decryption in Caesar cipher is done by shifting letters in the opposite direction of encryption.

The modulo operator is used to encrypt and decrypt messages with a key from 0 to 25.

Each letter in the alphabet is assigned a number, and the modulo operation is applied with the key.

The encrypted message is converted back to the original using the modulo operator and the key.

The modulo operator helps in handling values that exceed the alphabet's range.

The video provides a step-by-step example of encrypting the word 'cryptography' using Caesar cipher.

An example of decrypting a message encrypted with a Caesar cipher is demonstrated.

The video explains how to encrypt the message 'mmw is fun' using the modulo operator with a key of five.

Decrypting an encrypted message using the modulo operator involves reversing the encryption process.

The video concludes with examples of both Caesar cipher and modulo operator encryption and decryption.

Transcripts

hi guys in this video we will be

discussing cryptography

so encrypting and decrypting messages

using two methods

cesar cipher and modulo operator

so let us define what is the meaning of

cryptography so the word cryptography

originated from the two pre-words crypto

which means hidden and graphene which

means writing so therefore the meaning

of

cryptography is hidden writing so

secret message to someone

you will use cryptography okay it is

making or breaking of secret codes

it uses two processes namely encryption

so for example nothing encryption

the process of transforming plain text

into code form

using a certain algorithm

plain text into codes and tagden guys

encryption

okay decryption

the process of converting back the

hooded message into plain text

hidden message that is called decryption

okay

so there are two methods in cryptography

shift cipher or caesar cipher

and then the next one is using a modulo

operator

so maritime natal key in cryptography he

refers to the strings of information

that is used to reveal the encrypted

message into readable

form so palaging cryptography

[Music]

cipher method so we i have two examples

here

is an encryption decryption okay so

not being determination example one use

the key of shift of three

so navigation and key to the right

so to the right and encrypt the word

cryptography

cryptography going hidden message

cryptography

[Music]

[Music]

[Music]

so one two three that is s and then

t one two three so w

o one two three so r

and then young g would be between g so

one two

three magnitude and then r

[Music]

letter b okay so that would be your

final answer

okay so again you told us

five shifts to the left and gaga with

more eye

five shifts to the right okay five

shifts to the

right and going to the left back

decryption guys opposite noun

encryption i decryption new encryption

so

you will do the opposite so eto

magicking instead of three to the right

decryption making

three to the left

one two three

okay

um you will do the opposite direction so

it was

to the left so gagawinko five to the

right

decryption okay so

nagawata do the opposite

direction okay so i'm adding um code

name

is b j y d n so b

j y d n

b j j y okay

so five to the right since in um

description decryption though

so since i've been left going right so

five dow

so young b it will be so one two

three four five so jito

yan and then on j so start also j

so five to the right one two three four

five so letter o

and then your y so one two three

four five so letter d so on first word

nothing is god

and the letter d a one two three

four five so i and a new end

one two three four five so that is s

and then b actually marinated so g n

and then in j marinara and j o okay so

that is letter o

so o and then j ulets o little and then

why maranatha

diane

guys sister cipher to have so paganic

the decrypt is our cipher

pack decryption you do the opposite pag

encryption

you follow the direction okay

let's have the manual second method

using modulo operator

so the center of the message uses the

key to encrypt

and to decrypt the secret message the

key may have any integer value from 0 to

25

and will this will be shared to the

person who will receive

the secret

[Music]

mmw is fun so we have we will encrypt so

original text or plain text

documentation code

so encrypt the message mmw is fun using

module operator so let k

is equal to five okay

okay so we have um 26 letters pero guys

must start cases 0

and um number so 0 25 per 26

0 so m is 12 okay

so 12 and then w is 22

i am and then i is

8 and then s is 18

f is 5 u

is 20 and then n is

13 i ayan okay now i'm gonna go in

parama using module operator

five okay so i will add five

to one of each so omega 105.

so 12 plus 5 is that was seventeen then

twenty-two plus five is twenty-seven

okay

and then eight plus five is thirteen

eighteen plus five is twenty-three five

plus five is ten

twenty plus five is twenty-five and 13

plus 5 is 18.

okay

[Music]

guys

okay and then 27 1272 guys okay so gente

gamet and modulo operator so modular

operator nothing is y is equal to

c c plus k

okay mode or mod 26

and package 26 because they marine time

26 um letters in an alphabet

okay so meron 26 channel 25 bian

queso pero 26

27 okay and then mode or mod

26 so the balance

my remainder

then you go is guys so 25 to the ba

since 27 though

so 25 so 89 26 89 27.

it's up to you guys 27.

okay so again next one 13 so 30 nothing

is n

and then 23 is x okay 10

is um k

ok 25 satoshi letter z and then 18

is s i n so i'm adding um

encrypted word is rrb and

x k z s

[Music]

is equal to five okay so

let's have the man um ganito paren so

encryption paren encrypt the message

i love you and then okay naman is ten

okay so surat kumar i love you so i

love you

i am okay so you ain't nothing is eight

and then el nathan is eleven

o is fourteen v is 21.

is four young y is 24.

is 14. is 20.

okay and again is 10 so i will add 10

so 10 okay

okay so 18

this one is 18 this one is 21.

this one is 24. so number 9

32 i 31

this one is 14. the lemon is 34.

so 24 and then i 30. okay

so

31i so when i'm 31 the guy says hang on

25 so you can use modulo so y

is equal to 31 okay modulo

um 26 okay lagging mode 26 huh

okay so 31 divided by 26 so ilang 31

meron ilang 26 marines are 31

26 31 so

31 minus 26 sumeromatite on

25 26 27 28

29 30 31 ion so 31

f okay next one 14 so 14

is zero i sorry zero oh okay and then 34

again will attain 34

34 34

over 26 so a long 26

[Music]

34-26 so eight

so on remainder kodi to i eight okay

okay so letter i okay and then 24 is

letter y

and then 30 again when i'm assigned 30

so y is equal to

30 mode um 26

so 30 divided by 26 so meron is on 26

30 and then 26 liters of 30

25 26 27 30 31 32 33 34 are you another

aisha again

okay so you isn't a man um 30

i am so 25 26 in the seventh eighth to

the ninth thirty so letter isha

so same okay so it's up to you so it is

final

[Music]

so decrypt the message rrb and xkz

let k is equal to five so nothing

but a hidden message rrb

[Music]

so like i call it in letters now your

numbers now so 17

17 young b is one young endaman

is 13 young x i 23

young k i 10 yong zhi

25 and then si18 guys pak decryption

sister cipher the bag opposite son

17 minus 5 that is 12.

so 12 1 minus 5 is negative 4 give me a

negative 4

and 13 minus 5 that is 8.

23 minus 5 is 18

10 minus 5 is 5 25 minus 5 is 20

and 18 minus 5 is 13

okay so 13.

12

negative one negative two negative three

negative four negative five pagoda

negative two negative three negative

four negative five sila yoon

hang gang negative 26 okay

so this one would be uh negative

four so negative four coi w i n

okay i

and then five is f

and then 20 is you and then your 13 is

in actually

example nothing to say one r

[Music]

so the hidden words or the hidden

sentence is mmw is

fun okay let's have the last example of

decryption using modulo

so decrypt the message s v

y f o i y

e okay so k is equal to 10 so an

uncommon a young s nothing is 18

v naman is um 21

y is 24 young f is five

and o is fourteen vietnam

ayan ai naman is eight and then y

is 24 and then e i four so since

decryption though instead of

i'm adding i will

[Music]

okay so 18 minus 10 is 8 21 minus 10 is

11

24 minus 10 is 14 5 minus 10 is negative

5

14 minus 10 is 4 8 minus 10 is negative

2

24 minus 10 is 14 and 4 minus 10 is

negative

6. okay so pog negative guys negative

huh

like again you're negative but

nothing

negative five so negative one two three

four five so that is letter v

okay young foreign e

okay your negative 2 so negative 1

negative 2 that is

y and then your 14 iso

and a negative 6 so negative 1 negative

2 negative 3 negative 4 negative 5

negative six so letter u actually

s v y f o i y e and y encrypt

s v y f o i y e so the next

i love you so same answer okay

so that is it for the um cryptography

okay um

[Music]

shift cipher or cesar cipher

[Music]

okay so that is it for the cryptography