Question

- explain how the pseudo one-time pad works? What are its limitations?

Answer 1

The One-time pad:

One-time pad (OTP) is also called as Vernam-cipher or we can say that it is the perfect cipher and it is a crypto algorithm in which the plaintext is combined with a random key. It is the only existing mathematically unbreakable encryption.

In cryptography, the one-time pad (OTP) is an encryption technique, it is not possible to crack it, but requires the utilization of a one-time pre-shared key the same size as or longer than the message being sent. In this technique, a plaintext is paired with a random secret key (also referred to as a one-time pad).

One-time pad cipher is a kind of Vignere cipher it includes the following features

• It is not possible to crack the cipher

• The length of the message which is encrypted is same as exactly key

• The key is made up of random symbols.

• As the name suggests, the key is used one time only and it is never used again for any other message to be encrypted.

How the pseudo one-time pad works?

Step 1-Create the Key:

Step 2: Format your Message:

Step 3: Encrypt your Message:

Step 4: Decrypting the Message:

here in this image I have explained how encyrption and decryption done by example :

one more example on enryption using a One-time pad :

same example for decryption  using a One-time pad :

note subtraction is applicable only for the number which is greater than 25

Limitaions :

1. the key is as long as the message.

2.only secure if each key is used to encrypt a single message.