**Encryption **is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot Decryption: The process of unlocking the encrypted information using cryptographic techniques Key: A secret like a password used to encrypt and decrypt information. There are a few different types of keys used in cryptography. An algorithm: is basically a procedure or a formula for. An encryption algorithm is a set of mathematical procedure for performing encryption on data. Through the use of such an algorithm, information is made in the cipher text and requires the use of a key to transforming the data into its original form.**Encryption types:**

1-Symmetric.

2-Asymmetric.

**Symmetric Encryption**

Symmetric Encryption: This is the simplest kind of encryption that involves only one secret key to cipher and decipher information. Symmetrical encryption is an old and best – known technique. It uses a secret key that can either be a number, a word or a string of random letters. It is a blended with the plain text of a message to change the content in a particular way. The sender and the recipient should know the secret key that is used to encrypt and decrypt all the messages.

Some of Symmetric Encryption Algorithms:

Blowfish, AES, RC4, DES, RC5, and RC6.

1- The most widely used symmetric algorithm is: AES – 128, AES – 192, and AES – 256. 2- The main disadvantage of the symmetric key encryption is that all parties involved have to exchange the key used to encrypt the data before they can decrypt it.

**Asymmetric Encryption**

Asymmetric Encryption is also known as public key cryptography, which is a relatively new method, compared to symmetric encryption. Asymmetric encryption uses two keys to encrypt a plain text. A public key is made freely available to anyone who might want to send you a message. The second private key is kept a secret so that you can only know.

A message that is encrypted using a public key can only be decrypted using a private key, while also a message encrypted using a private key can be decrypted using a public key Security of the public key is not required because it is publicly available and can be passed over the internet. Asymmetric key has a far better power in ensuring the security of information transmitted during communication .

1- Asymmetric encryption is mostly used in day – to – day communication channels especially over the internet .

2- Popular asymmetric key encryption algorithm includes: ElGamal RSA, DSA Elliptic curve techniques, PKCS.

**Symmetric Vs Asymmetric Encryption**

1- Symmetric encryption uses a single key that needs to be shared among the people who need to receive the message while asymmetrical encryption uses a pair of public key and a private key to encrypt and decrypt messages when communicating.

2- Symmetric encryption is an old technique while asymmetric encryption is relatively new.

3- Asymmetric encryption was introduced to complement the inherent problem of the need to share the key in symmetrical encryption model, eliminating the need to share the key by using a pair of public – private keys.

4- Asymmetric encryption takes relatively more time than the symmetric encryption.

**Asymmetric Encryption in Digital Certification**

1- To use asymmetric encryption, there must be a way of discovering public keys, One typical technique is using digital certificates in a client – server model of communication. A certificate is a package of information that identifies a user and a server. It contains information such as an organization’s name, the organization that issued the certificate, the users’ email address and country, and users public key.

2- When a server and a client require a secure encrypted communication, they send a query over the network to the other party, which sends back a copy of the certificate. The other party’s public key can be extracted from the certificate. A certificate can also be used to uniquely identify the holder.

3- SSL / TLS uses both asymmetric and symmetric encryption.

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