Digital signature:
(i) Digital signatures are based on asymmetric cryptography and can provide assurances of evidence to origin, identity and status of an electronic document, transaction or message, as well as acknowledging informed by the signer.
(ii) To create a digital signature, signing software (email) Creates a one-way hash of the electronic data to be signed.
(iii) The user's private key to encrypt the hash, returning a value that is unique to the hashed data. The encrypted hash, along with other information such as the hashing algorithm, forms the digital signature. Any change in the data, even to a single bit, results in a different hash value.

(iv) This attribute enables others to validate the integrity of the data by using the signer's public key to decrypt the hash. If the decrypted hash matches a second computed hash of the same data, it proves that the data hasn't changed since it was signed.
(v) If the two hashes don't match, the data has either been tampered with in some way (indicating a failure of integrity) or the signature-was created with a private key that doesn't correspond to the public key presented by the signer (indicating a failure of authentication).

Types of Encryption :
There are two types of encryption schemes as listed below: Symmetric Key encryption, Public Key encryption.
(i) Symmetric Key Encryption:
Symmetric encryption is a technique to use the same key for both encryption and decryption. The main disadvantage of the symmetric key encryption is that all authorized persons involved, have to exchange the key used to encrypt the data before they can decrypt it. If anybody intercepts-the key information, they may read all message. Depicts the working of symmetric key encryption.
(ii) Public Key Encryption:
Public key encryption is also called Asymmetric encryption. It uses the concept of a key value pair, a different key is used for the encryption and decryption process. One of the keys is typically known as the private key and the other is known as the public key. The private key is kept secret by the owner and the public key is either shared amongst authorized recipients or made available to the public at large. The data encrypted with the recipient's public key can only be decrypted with the corresponding private key. public key encryption

Software Piracy is about the copyright violation of software created originally by an individual or an institution. It includes:
(i) stealing of codes / programs and other information illegally and creating duplicate copies by unauthorized means and utilizing this data either for one's own benefit or for commercial profit.
(ii) Downloading software from illegal network sources.
An entirely different approach to software piracy is called shareware, acknowledges the futility of trying to stop people from copying software and instead relies on people's honesty.
Shareware publishers encourage users to give copies of programs to friends and colleagues but ask everyone who uses that program regularly to pay a registration fee to the program's author directly.
To prevent unauthorized access, Firewalls, Intrusion Detection Systems (IDS), Virus and Content Scanners, Patches and Hot fixes are used.