Unit 3- Question 1_Ngoc

To apply to the 12th grade computer program, the lesson “information and data security”. I have some coding examples to help with the lesson as follows

  1. The Caesar Cipher technique

The Caesar Cipher technique is one of the earliest and simplest method of encryption technique. It’s simply a type of substitution cipher, i.e., each letter of a given text is replaced by a letter some fixed number of positions down the alphabet. For example with a shift of 1, A would be replaced by B, B would become C, and so on. The method is apparently named after Julius Caesar, who apparently used it to communicate with his officials.

Thus to cipher a given text we need an integer value, known as shift which indicates the number of position each letter of the text has been moved down.

The encryption can be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,…, Z = 25. Encryption of a letter by a shift n can be described mathematically as.

Encryption Phase with shift n: En(x)=(x+n) mod 26

Decryption Phase with shift n: Dn(x)=(x-n) mod 26



Shift: 23



Shift: 4


  1. Cryptography in Blockchain

Blockchains make use of two types of cryptographic algorithms, asymmetric-key algorithms, and hash functions. Hash functions are used to provide the functionality of a single view of blockchain to every participant. Blockchains generally use the SHA-256 hashing algorithm as their hash function.

Hash functions have a major role in linking the blocks to one another and also to maintain the integrity of the data stored inside each block. Any alteration in the block data can lead to inconsistency and break the blockchain, making it invalid. This requirement is achieved by the property of the hash functions, called the ‘avalanche effect’.

According to this, if we make even a slight change in the input to the hash function, we will end up getting a totally unrelated output as compared to the original output. Let us take an example of an SHA-256 hash function, and compare their outputs,

* Present to students the application of Blockchain in several fields:

Secure personal information: Keeping data such as your Social Security number, date of birth, and other identifying information on a public ledger may actually be more secure than current systems more susceptible to hacks. Blockchain technology can be used to secure access to identifying information while improving access for those who need it in industries such as travel, healthcare, finance, and education.

Secure Internet of Things networks: The Internet of Things (IoT) is making our lives easier, but it’s also opening the door for nefarious actors to access our data or take control of important systems. Blockchain technology can provide greater security by storing passwords and other data on a decentralized network instead of a centralized server. Additionally, it offers protection against data tampering since a blockchain is practically immutable.

Data storage: Adding blockchain technology to a data storage solution can provide greater security and integrity. Since data can be stored in a decentralized manner, it will be more difficult to hack into and wipe out all the data on the network, whereas a centralized data storage provider may only have a few points of redundancy. It also means greater access to data since access isn’t necessarily reliant on the operations of a single company. In some cases, using blockchain for data storage may also be less expensive.

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