PKI Digital Sign Made Easy

Encrypt Electronic Signature Presentation Later

signatures have been used since time immemorial to establish identity and authenticate message signatures have undergone transformations in each error from impressions too intricate seals describing one's own name in this digital era signatures have manifested in the form of digital signatures armed with legal sanctity digital signatures are being adopted widely across applications domains and sectors let's see what the desired properties of a signature are a signature needs to provide assurance of identity of the signer that's authentication it needs to provide credible evidence that the signer had indeed involved in the act of signing and could not deny it later that's non repudiation it should also provide the assurance that the contents or data has not been modified since it was signed and that's integrity hence a digital signature has to achieve the aforesaid properties in a medium where copying and modification of a document or message is as simple as a click and where transfer of data is measured in seconds and that's the major challenge this is where the concepts of cryptography help us to firmly establish the authenticity of the digital signature integrity of the document and also provide the non-repudiation ability in a handwritten signature though the process of authentication is fairly simple and generally done by visual comparison with a specimens signature the reliability of the process is a question however exit all signatures provide a foolproof mechanism to authenticate a signature and that can be done by anybody without the need for any previous or specimen signature there are two cryptographic concepts used in the process of digital signing one cryptographic hash functions that produce a fingerprint also known as message digests of the input message or document every time producing the same fingerprint for the same message any change to the input message will produce a very different fingerprint another most important characteristic of hash functions is that one cannot retrieve the original input using the fingerprint it is very much similar to a fingerprint of an individual that captures the uniqueness of an individual like a fingerprint cannot be used to create a sketch of the individual a message digest cannot be used for constructing back the original message hash functions are used in many applications including the ones that we use daily for logging in where only the hash value of the passwords is stored in the application the second cryptographic concept that comes to play is a symmetric key cryptography in a symmetric key cryptography algorithms such as RSA DSA and similar ones use two large prime numbers for generating public and private keys this key pair functions in a very unique way that is if you encrypt a message with one of the keys you can decrypt the message only by using the other key one of the keys is kept private while the other key can be shared to anybody and is referred as the public key an analogy could be a lock with a...