Implementation of Digital Signature Authentification Process

One of the benefits of doing business in cyberspace is that it can do transactions anytime and anywhere without having a physical face to face between seller and buyer. However this is often a problem in itself, especially related to authentication problems. How the seller can be sure that the purchased product is a real person (like a confession)? How the seller can be confident, for example:• That the credit card that is used is really the property of the purchaser? or• That the information submitted by the seller does not fall into the hands of those who are not eligible unless the buyer is concerned? or• That the documents sent are not altered by those who have no right in the middle of a transmission line? or• That the trade transaction can be legally valid in the absence of the fraud of the buyer?• and so forth.
In the real world, usually to solve this problem use "signature" as proof of authentication (authenticity) identification of a person. In the virtual world, offered a concept that is named as "Digital Signature" or a digital signature (Kosiur, 1997). The principle of implementing a digital signature system is as described below.
In contrast to the method "public-key encryption" which technically requires a relatively long time to do the encryption (random coding) of a document, the digital signature system, a document that is sent is not encrypted using the public key (public key).Source: David Kosiur, 1997.The document is encoded using a mathematical function called "Hash Function". Using Hash Function type 16 bytes, then the long text that will be expressed in 16 fruit characters, such as: CBBV235ndsAG3D67 named as a "message digest". The sender then by using his personal code (private key) to encrypt a message digest, and the result is a digital signature (digital signature) from the sender. Digital signature is then combined with the existing text (original document) to then be sent over the Internet.
On the receiving party will be held a series of authentication processes. The first process is to separate the original documents with digital signatures attached to them. The second process is to re-enact the Hash Function against the original document to obtain the 16 character message digest. The third process is to perform the decryption process of the digital signature using public key (public key) from the sender. The next process is to compare or mengkomparasikan 16 character message digest results Hash Function and decryption activity. If the two message digests are identical, then the document and digital signature received is authentic, comes from the person in question and no unauthorized intervention in the course of transmission. Conversely, if it turns out the second message digest is not the same, meaning there are three possibilities occur:• Documents submitted has undergone changes in terms of content;• Digital Signature that was sent has been modified, or• Both have been amended so it is not the same as the original.
Of course these changes can occur due to intentional or not. Intentional in the sense of the word that someone or other parties who attempt to change or falsify documents digital signature; accident within the meaning of the word is possible "damage" Technically, both hardware and software, along the transmission medium so that there is a change of data sent. The only problem of this authentication method is sending the original documents without having to do the encryption (as it is considered slow, especially if the document contains a very long text). But the concept of "pareto" can be used, within the meaning of applying the assumption that 80% of communication is "safe." If what happened with "intervention" in the transmission line, the second alternative is the use of "symmetric encryption" or "public-key encryption" can be used as an alternative.

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