Kaid's Blog

A Case Study On End-to-End Encryption Used In Whatsapp 1.Introduction to End-to-End Encryption WhatsApp's end-to-end encryption is available when you and the people you message use the latest versions of the app. WhatsApp's end-to-end encryption ensures only you and the person you're communicating with can read what is sent, and nobody in between, not even WhatsApp. This is because your messages are secured with a lock, and only the recipient and you have the special key needed to unlock and read them. For added protection, every message you send has its own unique lock and key. WhatsApp, since its inception six years ago, has quickly grown into a global phenomenon, becoming one of the most popular mobile based communications applications in the world today. With a user base that eclipsed one billion in February, WhatsApp provides a service that potentially endangers the privacy of over 10% of the entire human population. In order to address these security concern...

Columnar Transposition Cipher Introduction  The columnar transposition cipher is a fairly simple, easy to implement cipher. It is a transposition cipher that follows a simple rule for mixing up the characters in the plaintext to form the ciphertext. Although weak on its own, it can be combined with other ciphers, such as a substitution cipher, the combination of which can be more difficult to break than either cipher on it's own. The  ADFGVX cipher uses a columnar transposition to greatly improve its security. Example  The key for the columnar transposition cipher is a keyword e.g.  GERMAN . The row length that is used is the same as the length of the keyword. To encrypt a piece of text, e.g. defend the east wall of the castle we write it out in a special way in a number of rows (the keyword here is  GERMAN ): G E R M A N d e f e n d t h e e a s t w a l l o f t h e c a s t l e x x In the above example, the plaintext has been padded so that ...

Convolution Convolution is a mathematical way of combining two signals to form a third signal. It is the single most important technique in Digital Signal Processing. Using the strategy of impulse decomposition, systems are described by a signal called the impulse response. Convolution is important because it relates the three signals of interest: the input signal, the output signal, and the impulse response. This chapter presents convolution from two different viewpoints, called the input side algorithm and the output side algorithm. "Circular convolution The  circular convolution , also known as  cyclic convolution , of two aperiodic functions (i.e.  Schwartz functions ) occurs when one of them is  convolved in the normal way  with a  periodic summation  of the other function. That situation arises in the context of the  Circular co nvolution theorem .  The identical operation can also be expres...