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Everything has a Signature

Every data has a signature which can be derived mathematically. All data of any size can be digested into fixed-size signatures. The signatures can be used to identify the data. Unique data has unique signature.

Cryptographic hashing is a mathematical technique to hash or digest a data to reveal its signature. Digesting the same data always produce the same signature. Any minor change on the data will produce significantly different signature. A changed data is a different data.

Data signature, hashing or digesting makes it possible for the data to be represented by its signature into a subsequent signing by combining it with one or more data signatures to produce a new signature representing a larger data set. Eventually, all data can be digested in chunks to produce a single signature.

A signature can be verified by hashing the same data again which will produce the same signature. This introduces data signing-verification concept. In a communication between two parties, the first party starts by hashing a data set to produce the signature. Then he packs both the data set and the signature and send them to the second party. On arrival, the second party will hash the data set and compare the signature with the one given by the first party. If the signatures match then the data set will be treated as complete and original.

The data signing-verification approach as mentioned above will work when there is no harm on the communication channel. A man-in-the-middle may simply change the data set and the signature. Hence, the public-key cryptography was introduced where the data set will be securely signed by the first party using a private key, and to be verified by the second party using a public key. Only the first party can sign the data set since he keeps the private key secret, and anybody with the public key can verify it. The first party will always keep his private key secret, and distribute the public key only to relevant parties.

This particular public-key cryptographic technique encrypts a data signature using a private key to produce encrypted signature. The encrypted signature can only be decrypted using a public key to reveal the original signature. Note that secure data signing has nothing to do with data encryption. It is up to the parties to encrypt the data during communication.

Data signing goes deeper. Proof-of-work (PoW) signing or digesting is a kind of hashing algorithm which requires very high computing power so that a signature becomes very expensive to produce, yet very fast to verify. The idea is to make rehashing unfeasible, and in turn to prevent the data set from being altered at all. A chain of PoW signing will make the data sets even more highly unfeasible from being altered. This leads to eternal data which is a new asset class of information technology.

Data signature is a property that every system must not ignore.

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