05-10-2016, 03:32 PM
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Introduction
A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or documents.
A valid digital signature gives a recipient reason to believe that the message was created by a known sender
History
In 1976,whitfield diffi and Martin Hellman first described the notion of a digital signature scheme.
Soon afterwards, Ronald Rivest,Adi Shamir, and Len Adleman invented the RSA algorithm, which could be used to produce primitive digital signatures
Other digital signature schemes were soon developed after RSA, the earliest being Lamport signatures,merkel signature
Encryption
Encryption is the conversion of data into a form, called a CIPHER Text.
The use of encryption/decryption is as old as the art of communication.
Encryption/decryption is especially important in wireless communications.
Encryption/decryption is a good idea when carrying out any kind of sensitive transaction
Types of Encryption
Private key encryption
Private key means that each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent over the network to the other computer.
Public Key encryption
Public key encryption uses a combination of a private key and a public key.
The key is based on a hash value. This is a value that is computed from a base input number using a hashing algorithm.
What is a digital signature?
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document.
A digital signature can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact.
Creation of Digital Signatures
A digital signature scheme typically consists of three algorithms:
HASHING algorithm.
Signature Generation Algorithm
A signature verifying algorithm
Hashing
Hashing is the transformation of a string of characters into a usually shorter fixed-length value or key that represents the original string.
As a simple example of the using of hashing in databases, a group of people could be arranged in a database like this:
Abernathy Sara, Epperdingle Roscoe, Moore Wilfred, Smith David (and many more sorted into alphabetical order)
After Hashing, each of them will be replaced by a 4 digit number (in this case)
Hashing Algorithm
The formula for hashing depends on two inputs:
the sequence of characters representing the electronic data to be signed
a secret number referred to as a signature's private key associated with the signing party and which only that party has access to
Some simple Hash Functions
The division-remainder method
Folding
Radix transformation
Digit rearrangement
Methods of Encryption based on Privacy
Encryption scrambles or modifies a message or document so it cannot be read and understood, except by the intended recipient.
A key is necessary to reverse the scrambling or modification, to make the message readable.
Methods of Encryption based on Privacy are as follows:
a message may be digitally signed, but not encrypted
a message may be encrypted first, then digitally signed
a message may be digitally signed first, then encrypted
Digital Signature Verification
It is the process of checking the digital signature by the reference to the original message and a given public key.
Verifying also relies on a formula. Here, the formula depends on three inputs:
The sequence of characters representing the supposedly originally signed electronic data
The public key of the signing party
The value representing the supposedly authentic digital signature.
The output of the formula is a simple answer: YES or NO.
Digital Signature Schemes
The following are the widely used Schemes for Digital Signatures
RSA Scheme
ElGamal Scheme
Schnorr Scheme
Digital Signature Standard (DSS)
Legal Aspects of Digital Signatures
The digital signature is that which makes a document a legal one.
It is a representation of assuring that the document meats all legal and is authentic in its framework.
The actual digital signature provides the following:
• Evidence
• Ceremony
• Approval
• Efficiency
Advantages of Digital Signatures
Authentication, identification of the person that signs.
Integrity of data, every change will be detected.
Non repudiation, because the author cannot
be denied of his work (he created and sent).
Imposter prevention
Elimination of possibility of committing fraud by an imposter
Disadvantages
The disadvantages of using digital signatures involve the primary avenue for any business: money.
Though the use of Digital Signatures is very powerful way to secure and authenticate a message or document, its advantages are hampered by lost or theft of keys and the use of vulnerable storage facilities.
A number of Digital Signature standard exist which are incompatible with each other and there is a strong need of a standard through which these different methods (keys) can interact.
Applications of digital signatures
As organizations move away from paper documents with ink signatures or authenticity stamps, digital signatures can provide added assurances of the evidence to provenance, identity, and status of an electronic document as well as acknowledging informed consent and approval by a signatory. The United States Government Printing Office (GPO) publishes electronic versions of the budget, public and private laws, and congressional bills with digital signatures. Universities including Penn State, University of Chicago, and Stanford are publishing electronic student transcripts with digital signatures