CRYPTOGRAPHY
Cryptography is a technique used to hide the meaning of a message and is derived from the Greek word Kryptos (hidden). If a message were to fall into the hands of the wrong person, cryptography would ensure that that message could not be read.
Typically the sender and receiver agree upon a message scrambling protocol beforehand and agree upon methods for encrypting and decrypting messages.
This makes Cryptography —Inherently defensive in securing information sent from one party to another. “If you know the secret to a piece of cryptography, you can decipher the message. If you do not know the secret, you will have to guess every possible secret.” -Gigi Der
History of Cryptology
Manually
There have been three well-defined phases in the history of cryptology. The first was the period of manual cryptography, starting with the origins of the subject in antiquity and continuing through World War I. Throughout this phase, cryptography was limited by the complexity of what a code clerk could reasonably do aided by simple mnemonic devices. As a result, ciphers were limited to at most a few pages in size, i.e., to only a few thousands of characters. General principles for both cryptography and cryptanalysis were known, but the security that could be achieved was always limited by what could be done manually.
Mechanically
The second phase, the mechanization of cryptography, began shortly after World War I and continues even today. The applicable technology involved either telephone and telegraph communications (employing punched paper tape, telephone switches, and relays) or calculating machines such as the Brunsvigas, Marchants, Facits, and Friedens (employing gears, sprockets, ratchets, pawls, and cams). This resulted in the rotor machines used by all participants in World War II. These machines could realize far more complex operations than were feasible manually and, more importantly, they could encrypt and decrypt faster and with less chance of error. The secure size of ciphers grew accordingly so that tens or even hundreds of thousands of characters were feasible. The switch from electromechanical devices to electronic ones accelerated this trend.
Electronically
The third phase, dating only to the last two decades of the 20th century, marked the most radical change of all—the dramatic extension of cryptology to the information age: digital signatures, authentication, shared or distributed capabilities to exercise cryptologic functions, and so on. It is tempting to equate this phase with the appearance of public-key cryptography, but that is too narrow a view. Cryptology’s third phase was the inevitable consequence of having to devise ways for electronic information to perform all of the functions that had historically been done with the aid of tangible documents.
History and Evolution of Cryptography and Cryptanalysis
Bitcoin & Cryptography
Cryptographic Functions
Bitcoin utilizes cryptography in a couple of ways. It uses cryptographic hash functions to generate digital signatures PRIVATE & PUBLIC KEYS, (just like a physical signature) yet way more secure. This is what connects approval of the data (bitcoins) being signed to the specific identity of the signer. SO if anyone ever asks if you have the private key ( the secret) for a specific public key address, (publicly known) you can give them a digital signature to prove it.
The Bitcoin network itself does not use any encryption specifically. As an open, distributed database, the #blockchain has no need to encrypt data. All data passed through the network from node to node is unencrypted, allowing anyone to interact over the Bitcoin network.
However, #bitcoin uses cryptography most importantly by utilizing cryptographic Hash functions - which is a mathematical function that takes any data as INPUT and produces an OUTPUT with special characteristics. Bitcoin specifically uses the hash function type SHA-256, (256 bits) - a member of the Secure Hashing Algorithm family of hash functions.
The hash INPUT can vary infinitely, but the OUTPUT of a crypto hash function is always a certain length of characters. (256 bits of alphanumerical data.) A hash is not ‘encryption’ – it cannot be decrypted back to the original text (it is a ‘one-way’ cryptographic function, and is a fixed size for any size of source text) impossible to reverse.
