**There are many cryptographic techniques and protocols, they mostly**

fall into one of three categories:

fall into one of three categories:

**Bulk Encryption : This is the modern equivalent of secret writing . A bulk encryption algorithm uses a key to scramble (or encrypt ) data for transmission or storage. It can**

then only be unscrambled (or decrypted ) using the same key. Bulk encryption is so called because it is effective for securing large chunks of data. Some common algorithms are Data Encryption Standard (DES), Data Encryption Algorithm (DEA) and RC4. This is also called the symmetric encryption.

then only be unscrambled (or decrypted ) using the same key. Bulk encryption is so called because it is effective for securing large chunks of data. Some common algorithms are Data Encryption Standard (DES), Data Encryption Algorithm (DEA) and RC4. This is also called the symmetric encryption.

**Public Key Encryption :This is also a technique for securing data but instead of using a single key for encryption and decryption, it uses two related keys, called public key and private key , which together form what is known as a key pair . As the word suggests, public keys are made available to everyone, but each entity that holds a key pair should keep the private key as secret. If data is encrypted using one of the keys, it can only be decrypted using the other, and vice-versa.**

**Public key encryption is a form of asymmetric encryption, because the key that is used to encrypt is different from the key used to decrypt. With this technology, the sender in a secure communication can use the receiver’s public key to encrypt the data, because at that point in time only the receiver can decrypt the data, by using its own private key.**

**Compared to bulk encryption, public key encryption is more secure, because it does not require the transmission of a shared key that both the parties must hold. However, public key encryption is computationally expensive and is therefore not suited to large amounts of data.**

**The most commonly-used algorithm for public key encryption is the Rivest,Shamir and Adleman (RSA) system.**

**Hashing : A secure hash is an algorithm that takes a stream of data and creates a**

fixed-length digest of it. This digest is a fingerprint for the data. A digest has two main properties:

1. If even one single bit of data is changed, then the message digest changes as well. Notice, however, there is a very remote probability that two different arbitrary messages can have the same fingerprint.

2. Even if someone was able to intercept transmitted data and its fingerprint, that person would not be practically able to modify the original data so that the resulting data has the same digest as the original one.

fixed-length digest of it. This digest is a fingerprint for the data. A digest has two main properties:

1. If even one single bit of data is changed, then the message digest changes as well. Notice, however, there is a very remote probability that two different arbitrary messages can have the same fingerprint.

2. Even if someone was able to intercept transmitted data and its fingerprint, that person would not be practically able to modify the original data so that the resulting data has the same digest as the original one.

**Hashing functions are often found in the context of digital signatures. This is a method for authenticating the source of a message, formed by encrypting a hash of the source data. Public key encryption is used to create the signature, so it effectively ties the signed data to the owner of the key pair that created**

the signature.

the signature.

**This all about Cryptographic Techniques and Protocols. We will discuss further in future articles in my blog. Thanks for reading friends.**

good work

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