Overview of Cryptography and Digital Signature

It is the technique of transmitting or storing the data by which only those person can read to Who it is planned for can process or read. Cryptography is the method in which we can protect the information by making the unreadable form of any plain text by encoding it. So with the help of this we can protect any sensitive information while transmitting it to one system to another system on network path or while storing it on any media...

The main working of cryptography is to prevent the sensitive information from any unauthorised access by using some encryption technique and decryption technique. There are most of the algorithm breaks by the attacker if they have sufficient time and resources to break it and then all the sensitive information be able to reveal by them. Main reason to introduce the cryptography is to make difficult for attacker to reveal the information.

This fig shows cryptography technique, in this figure firstly plain text is enter into encryption process by putting some encryption algorithm with the help of key it is converted into cipher text and then by putting it on decryption process with the help of key it is again converted into plain text. So by the help of these encryption technique and decryption technique both the sender and receiver get secure transmission of data because no one can easily break the encrypted text or cipher text.

So by cryptography we can achieve secure transmission of data, data integrity, data privacy, authentication of data and many other things. Because when the text is in encrypted format or in cipher text format it is in unreadable form and only authorised person can read it, so we can easily transmit it from one place to another place.

Goal of cryptography:

 Data Confidentiality: Only an authorized recipient should be able to extract the contents of the message from its encrypted form.  

 Data Integrity: The recipient should be able to determine if the message has been altered. 

 Authentication: The recipient should be able to verify from the message, the identity of the sender, the origin or the path it travelled (or combinations) so to validate claims from emitter or to validated the recipient expectations. 

 Non-Repudiation: The emitter should not be able to deny sending the message. 

How does cryptography work:

Cryptography is the technique of encryption and decryption by the use of combination of keys. With the help of key we can encrypt the plain text and convert it into cipher text and for converting that cipher text into plain text again we have to use the key to decrypt it. 

The privacy of cipher text is totally dependent on two things that you must have not share your key to any one and the strength of algorithm, these are the two things by which the security of encrypted data depends.

Encryption types:

In cryptography there are two types of encryption:

1.) Symmetric cryptography

2.) Asymmetric cryptography 

Symmetric cryptography:

Symmetric cryptography also known as secret key or private key cryptography and single key cryptography because in this type of cryptography both the parties uses same single key to encrypt or decrypt the text. Like if a user want to send encrypted message to another user then second user must have the key which is used by first user to encrypt the message so that second user can decrypt the message. In below fig first user sends second user a message that is hello Alice and the key which is used by the first user to encrypt the message is same key which is used by the second user to decrypt the message. This is fast technique to encrypt the information but there is a problem in this technique that is key exchange problem because while exchanging the key if it is compromised to any unauthorised person then he can use the information. So it is good technique but not reliable.  

Asymmetric cryptography:-

Asymmetric cryptography is also known as public key cryptography. In 1975 Whitfield Diffie and Martin Hellman introduce this type of cryptography technique to avoid the key exchange problem.

Asymmetric cryptography uses pair of keys to encrypt the plain text and decrypt the cipher text. In this technique sender sends message by encrypting it through its public key and receiver decrypt it by its corresponding private key. So in this technique you can publish your public key to anyone and keep your private key secret. Any person who encrypts any text through his public key cannot decrypt that text, only that person who have corresponding private key can only decrypt the text.

The main benefit of public key cryptography is that, users do not have to share their private key all transmission is done through public key you have to keep your private key secret. There is no need to share your private key to anyone. The asymmetric cryptography provides more security then symmetric cryptography but asymmetric cryptography is slower then symmetric cryptography and it is reliable.

 

Above figure shows that first user sends some information to second user, so first user encrypt the plain text into cipher text through public key to make it in unreadable form and transmit the information to second user then second user decrypt that cipher text into plain text by its corresponding private key and make it in readable form. 

SOME ALGORITHMS

 Hash based message authentication.

 Message digest [ MD2, MD4, MD5 ].

 Secure hash algorithm SHA1.

 RSA Rivest Shamir Adleman.

 DH Diffie- Hellman.

 DES data encryption standard.

 IDEA international data encryption algorithm.

 Lucifer

 AES American Encryption Standard.

 FEAL-N.

 Khufu and khafre.

 LOKI.

 Madryga.

 MMB.

 NewDES.

 RC2 and RC4.

 RES

Digital signature standard:

Digital signature is the encrypted hash value of a message. By digital signature we can get the detail that when and who send the message. Digital signature is used to sign message digitally. We can say that digital signature just serve the purpose of hand written signature. Hand written signature can easily be copied by any person but it is difficult to copy the digital signature that’s why digital signature is superior then hand written signature. 

RSA and DSA both are widely used algorithms. Unlike RSA, we can only use digital signature algorithm as a digital signature. RSA can be used for message encryption and digital signature both.

Advantages of Asymmetric Cryptography:

1.) In asymmetric cryptography public key can be shared worldwide and private key must be kept secret.

2.) This technique provides more security then private key cryptography.

3.) The asymmetric key pair can remain unchanged for several years.

4.) RSA algorithm can be use for both encryption as well as digital signature.

Conclusion:

Cryptography is a best known and widely used thing in worldwide to encrypt and decrypt the message so that any unauthorised person cannot read the data. In symmetric or private key cryptography there is a problem of key exchange so asymmetric or public key cryptography is introduced in which we can share public key widely but keeping the private key secret.