Symmetric and Asymmetric Encryption

KS3 Computer Science

11-14 Years Old

48 modules covering EVERY Computer Science topic needed for KS3 level.

GCSE Computer Science

14-16 Years Old

45 modules covering EVERY Computer Science topic needed for GCSE level.

A-Level Computer Science

16-18 Years Old

66 modules covering EVERY Computer Science topic needed for A-Level.

KS3 Encryption Algorithms (14-16 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module

A-Level Compression, Encryption and Hashing (16-18 years)

  • An editable PowerPoint lesson presentation
  • Editable revision handouts
  • A glossary which covers the key terminologies of the module
  • Topic mindmaps for visualising the key concepts
  • Printable flashcards to help students engage active recall and confidence-based repetition
  • A quiz with accompanying answer key to test knowledge and understanding of the module


There is an ever-current chance of inappropriate access to all kinds of data in today’s cyber globe. Financial and payment system information that tin show consumers’ and customers ‘ personal identification information (pii) or payment card data is most at risk. encryption is important for securing pii and reducing the threats faced every minute of the day by organisations that perform payment transactions.

What is Symmetric Encryption

Symmetric encryption is a method of encryption where electronic communication is twain encrypted and decrypted using just one key (a hidden key). The key must be shared between individuals communicating through symmetric encryption so that it can be utilised in the procedure of decryption. This procedure of encryption changes from asymmetric encryption, where a twain of pitch/keys is used to encrypt and decrypt messages, one public and one private. data is transformed to a shape that cannot be interpreted by someone who does not hold the hidden key to decode it by using symmetric encryption algorithms.

The algorithm reverses its operation until the intended receiver who owns the key has the address so that the address goes back to its real and comprehensible form. a particular password/code tin be the secret key that twain the exporter and the recipient utilisation, or it may be an arbitrary cord of characters or digits created by a stable arbitrary digit product (rng). The symmetric keys must be produced for banking- year encryption using a ring that is accredited according to manufacturing level, such as fips 140-2. This is the easiest type of encryption, consisting of only one personal key to encode and decode details. A traditional and well-known method is symmetrical encryption. a private key that tin be further a digit, a phrase, or an arbitrary character cord is used. to change the material in a certain manner, it is merged with the plain text of a document. the exporter and the recipient should be familiar with the private key used to encrypt and decode both communications.

Symmetric and Asymmetric Encryption: Symmetric Encryption model.

Definition of Symmetric Encryption

Symmetric cryptosystem (or private key cryptosystem) utilizes just one key for both encryption and decoding of the information. The key used for encryption and decoding is known as the private key and just individuals who are approved for the encryption/unscrambling would know it. in a symmetric cryptosystem, the scrambled message is sent over with no open keys connected to it.

Uses of Symmetric Encryption

Although symmetric encryption is an earlier encryption procedure, it is simpler and more effective than asymmetric encryption, which takes a charge on networks due to data area and weighty use of CPU speed problems. symmetric cryptography is normally utilisation for volume encode/encrypting massive volumes of data, e.g. for batch file encode, because of the improved correctness and greater speed of symmetric encode (compared to asymmetric). In the case of a database, the hidden key is only accessible to encrypt or decode the batch file itself.

There are some examples of where symmetric encryption is used:

  • Applications for amount, such as board purchases in which PII must be secured to escape identification theft or treacherous fee
  •  Attestation to prove that who he wants to be is the sender of a message
  •  Generation or hashing of random numbers

Components of Symmetric Encryption

Symmetric encryption scheme has five primary components: plaintext, encryption algorithm, hidden key, ciphertext, and the algorithm for decryption. one at a time, let’s look at these.


The word plaintext refers to the initial document that the encryption process produces and delivers. Because you’re attempting to encrypt it, it’s more possible that the plaintext holds confidential details that prying eyes may not see. The sample pictures of symmetric encryption provides a clear instance of how symmetric encryption works.

Encryption Algorithm:

The bonanza for encryption accepts the plaintext and transforms it into an indistinct design. Changing all Ns to a 3 will be a clear example of an encode bonanza or all Zs to a 1. Many passes and variations, called agreement, on the plaintext, can be done by the method. You’ll need a key until it’s encrypted to activate it.       


Think of the key as a decoder ring: without the key, it is hard to decipher the hidden of the scrambled document. On all the buttons and commutations made to the real plaintext, the key holds the information. In symmetric encode, the algorithm is actually packaged with the key; the decoder loop is not global in this case. The modifications and substitutes turn on the key, and vice versa since the key is exchanged between the sender and the receiver.


The text which is now encoded and ready to be submitted is the ciphertext. It can appear like a stream of data at random, and it is unreadable. 

Decryption Algorithm:

The Hidden Key is added to the ciphertext in the decryption algorithm. It transforms back to plaintext, effectively doing back-end encryption.   

Types of algorithms in symmetric encryption

Two kinds of symmetric encode bonanza exist:

Algorithms Block:

Using a particular hidden key, the set extent of bits are encoded into chunks of computerised data. While the data is encrypted, as it waits for full blocks, the device keeps the data in its memory.  

Algorithms for streams:

Instead of being preserved in the memory of the machine, data is encrypted as it streams.

Advantage and Disadvantage of Symmetric Encryption


  • A message can be decrypted by a device that only has a hidden key.
  • Faster is a symmetric cryptosystem.
  • Encrypted data may be passed to the connexion in Symmetric Cryptosystems, also though there is a risk that it will intercept the information. There isn’t any because there is no odds of data being decrypted are 0 with the key sent with the data.
  • A symmetric cryptosystem uses protection of passwords to establish the identity of the consignee.   


  • Symmetric cryptosystems have an issue of key transportation. The mystery key is to be communicated to the getting framework before the real message is to be sent. Each mean of electronic correspondence is unreliable as it is difficult to ensure that nobody will have the option to tap correspondence channels. So the main secure method of trading keys would trade them actually.
  •  Can’t give computerised marks that can’t be renounced   

 Example of Symmetric Encryption

Here are some examples where symmetric encode is used

  •  AES
  •  DES
  •  IDEA
  •  Blowfish
  •  RC4
  •  RC5
  •   RC6


DES was the initial structured code for controlling computerised information in “new” computing and is utilised in combinations. The real DES is no longer used since, due to the computing strength of the latest computers, it is deemed “too slow.” Even NIST and PCI DSS 3.2 do not suggest 3DES, much as all 64-bit codes. 3DES is quite used heavily in EMV bit cards, though.   

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The latest Encryption Standard (AES), which was really called as Rijndael, is the most widely used symmetric contrivance. The norm set by the U.S. In 2001, the national institute of standards and technology declared the encryption of computerised records in the United States. PUB 197 of the FIPS. This model replaces DES, which has been in utilisation since 1977. The AES code has a block area of 128 bits under NIST, but as seen with AES-128, AES-192 and AES-256, it may have three distinct key lengths.

Symmetric and Asymmetric Encryption Image 2

Key management for symmetric encryption

Sadly, a symmetric cipher does come with its own disadvantages. Its weak point is its main control elements, including:

Key Exhaustion:

Symmetric cypher suffers from nature in which any utilisation of a key ‘leaks’ any details that a killer may probably utilise to recreate the key. Both of these methods require professional key recovery methods to be traceable as if a discarded encryption key cannot be retrieved (for example), the data is theoretically lost. 

Attribution Data:

Symmetric keys do not have embedded metadata to document details such as expiry date or an entry Control record, unlike asymmetric (public-key) certificates, that show how the key should be used, for example, that cipher but not decode. The latter problem is solved more by guidelines such as ANSI X9-31, where a key may be connected to the knowledge that prescribes its utilization. But a key management scheme is required for complete power of what a key can be utilised for and when it can be utilised.

Key Management at large scale:

Where only some keys (tens to low hundreds) are involved in a system, the expenses power is minimal and can be controlled by manual, human operation. However, monitoring the expiration and organizing the exchange of keys easily becomes inefficient for a broad estate.


A very difficult activity is managing large-scale symmetric encryption schemes. This is extremely true where the organisational and/or IT infrastructure is decentralized / geographically dispersed, where we try to achieve banking-grade security and audibility.

To do this correctly, it is advocated that particular programs be used to preserve the correct life-cycle for each generated key. It is truly difficult to perform key management manually in instances of large key enrollment. For it, we need advanced core life-cycle management tools.

Over the next 5-10 years, quantum computation is expected to materialize. Based on today’s information, NIST already suggests replacing the commonly used 3DES contrivance with contrivances that we consider to be better.

We forcefully guide banks to move to a crypto agile setup, not understanding what advancement in machinery and thus in the development of malicious decryption contrivances might be. Such a configuration would make it easier to easily substitute algorithms with algorithms that are known to be more reliable when vulnerabilities are found. Decisions on investment and design need to be made now in order to prevent serious loss in the coming years.

What is Asymmetric Encryption

It gets more difficult and symmetric encryption by linking to a website on the public internet, by itself, would not work because the other end of the connection is not managed by you. How do you share a hidden key with each other without the possibility of it being detected in the middle by anyone on the internet?

Public key cryptography is otherwise called Hilter kilter encryption which is utilised as an instrument to ensure the mystery, unwavering quality which non-renouncement of electronic messages and safeguarding of records. Public-key encryption, a mix of a private key and a public key, utilizes two separate keys immediately. The private key must stay exclusive to its individual holders, while the public key must be made open to anybody by a library or vault that is unreservedly available. A machine may utilize the public key, given by the starting gadget, and its own private key to decode an encoded message. While a message sent starting with one gadget then onto the next would not be secure since the public key utilised for encryption is accessible and open to everybody, without the private key, somebody who gets it won’t read it.

The fundamental pair depends on long-length prime numbers. In a similar numerical strategy, both the general population and private keys are determined together simultaneously utilizing “hidden entrance” capacities. The key component of “hidden entryway” capacities is that without unique information they are anything but difficult to process one way, and hard to figure the other way (discovering its reverse).

The primary downside to asymmetric cipher is that, as opposed to symmetric encryption, it is sluggish. This is due to the technical complexities of asymmetric cryptography which thus takes much more resources to manage computation. Owing to the computing power it requires to keep things running, it is not ideal for lengthy sessions.

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Definition of Asymmetric Encryption

Asymmetric encryption is a type of data cipher, also called a public-key cipher, where the cipher key (also known as the common key) and one the other side decode key (also known as the personal key) vary. Only with the matching personal key will a message encode with the common key be decoded. Mathematically, the common key and the personal key are linked, but deriving the personal key from the common key is computationally infeasible. A receiver, however, may broadly spread the common key. In order to encode messages for the receiver, anybody can use the common key and only the receiver can decode them.

How Asymmetric Encryption works

Two separate, although connected keys are used for Asymmetric Encryption. For encryption, one key, the Common Key, is used and another, the Personal Key, is for decode. The Personal Key is meant to be secret, as indicated in the term, so that only the authenticated receiver may decrypt the message.

With a simple asymmetric encryption example, let’s understand this.

Pretend you’re an intelligence organisation and you need to formulate a method to check in safely with your spies. You don’t need two-way contact, you only need regular, comprehensive updates coming in from them. They have their orders. Asymmetric encryption will allow the agents to build public keys to encode their data and a personal key back at the head office, which is the only way to decode all. It gives an incomprehensible form of one-way contact.

How are the two keys generated?

A cryptographic contrivance lies at the core of an Asymmetric cipher. This contrivance used a protocol for key creation to generate a key couple. Both of the keys are related to each other mathematically. From one algorithm to another, this relationship between the keys varies.

Basically, the algorithm is a mixture of two features: encryption and decryption features. To say the obvious, the encryption method encrypts the information and it is decrypted by the decryption feature.

Asymmetric Encryption in SSL/TLS Certificates

Both symmetric and asymmetric approaches are used for SSL / TLS and other digital certificates. Now, maybe you’re thinking, ‘Why both? Since it’s more stable, shouldn’t asymmetric cryptography be used? ‘Admittedly, it’s better, but it comes with a pitfall. Computational time is a huge limitation when it comes to Public-Key cryptography. When both sides implement verification and features, it greatly slows the process down. It is where the day is saved by symmetric encryption.

First, when two parties (in the case of SSL, browser and server) come across each other, by asymmetric encryption, they validate each other’s private and public keys. When the authentication is satisfactory and all know who they are referring to, the encryption of the data continues, saving considerable time and fulfilling the purposes of security and data security through symmetric encryption. This whole procedure is called a handshake for SSL / TLS.

Uses of Asymmetric Encryption

Typically, asymmetric encodes are used using digital signatures to verification records. A numerical signature is a cryptographic procedure that is used to verify a letter, script or digital record for verification and legitimacy. It is the numerical equivalent of a signature or marked seal written by hand.

Numerical signatures can generate a warranty of evidence of the origin, identification and rank of a computerized document, transaction or post, based on asymmetric cryptography, as well as acknowledgement of informed consent by the signer.

 It is also possible to extend asymmetric cryptography to applications in which multiple users can require to encode and decode text, including:

  •   Encode email-it is possible to use a common key to encode a text and a personal key to decode it.
  •   SSL / TSL cryptographic contracts often allow use of asymmetric encodes to create secure connections between websites and browsers.
  •   As customers have common keys that anyone can see and personal keys that are kept hidden, bitcoin and other cryptocurrencies are built on asymmetric cryptography. A cryptographic algorithm is used by Bitcoin to ensure that the funds can be invested by only the rightful owners.

Benefits Asymmetric Encryption

Asymmetric cryptography’s benefits include:

  •  As there is no need to swap keys, the key distribution dilemma is avoided.
  •  As private keys do not even have to be exchanged or exposed to others, confidentiality is improved.
  • Digital signatures are required to be used so that a receiver can prove that a text came from a single source.
  •   It facilitates non- disapproval, meaning that the dealer does not decline to deliver a reply.

Advantage and Disadvantage of Asymmetric Encryption


  •  In asymmetric or common keys, there is no requirement for cryptography to pass keys, thereby removing the problem of key delivery.
  •  Enhanced defense is the main value of public-key cryptography: It is never necessary for private keys to be shared or disclosed to others.
  •   Numerical designation that can be deny can be given


  •  Speed is a downside to using common key cryptography for encode, there are common hidden key encode techniques that are much quicker than any common key encode system currently available.
  •  He can’t decode the messages he gets if a person loses his private key.
  • Since public keys are not authenticated, no one really knows whether the entity listed belongs to a public key. Users must, however, check that their common keys belong to them.
  • If a hacker discovers the private key of a person, all of the person’s messages can be accessed by the intruder.

Asymmetric vs. symmetric cryptography

The essential qualification between these two encryption procedures is that uneven encryption calculations utilize two separate however related keys, one key to encode the information and another key to disentangle it, while symmetric encryption utilizes a similar key to execute the errands of encryption and unscrambling.

The longitude of the keys is another difference between uneven and symmetric encryption. The length of the arbitrarily produced keys is normally set at 128-bits or 256-bits in symmetric cryptography, contingent upon the degree of security that is required.

There may, nonetheless, be a numerical connection between people in general and private keys in hilter kilter encryption. Since programmers can hypothetically use this example to break the encryption, to have a similar level of assurance, unbalanced keys should be any longer. The distinction in key length is articulated to such an extent that an awry 2048-piece key and asymmetric 128-cycle key have pretty much an equivalent measure of security.

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