From 09feefc9f04b38420a198b6f69895b242832ad30 Mon Sep 17 00:00:00 2001 From: Kai Stevenson Date: Fri, 28 Oct 2022 17:36:28 -0700 Subject: changed the file structure --- src/writing/cryptography.php | 45 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 src/writing/cryptography.php (limited to 'src/writing/cryptography.php') diff --git a/src/writing/cryptography.php b/src/writing/cryptography.php new file mode 100644 index 0000000..6c36572 --- /dev/null +++ b/src/writing/cryptography.php @@ -0,0 +1,45 @@ + +

As the amount of life spent online continues to increase, a great deal of private information is naturally + being transmitted: banking details, medical records, business correspondences. Where once these exchanges of + data would have occured between a small set of individuals in a shared space, they now happen between + continents, through hundreds of servers and over complex network infrastructures. It is a system that cannot + be fully accounted for by any individual, and so the means of transmission are insecure--much like having a + letter transmitted by a series of couriers, the data is liable to be intercepted or modified. And so both + parties in the exchange take on a risk that may prohibit especially critical data from being sent. + Cryptography is the study of data obfuscation--a means of making a message readable only by some. It is the + answer to the question "when the means of transmission cannot be trusted, how can information be conveyed + securely?

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There are two classes of encryption: symmetric and asymmetric. Symmetric encryption allows a message to be + encoded and decoded with the same piece of information, or key. The ancient Caesar cipher is an example of + this; an arbitrary number acting as the key was agreed upon by both parties, and every letter in the message + was shifted through the alphabet by that amount. It could easily be decoded by anyone who knew the key by + simply shifting the letters backward through the alphabet. Simple algorithms such as the Caesar cipher are + vulnerable to various attacks due to the patterns that they create in the ciphertext. A given letter may + always be encoded in the same way, meaning that the key could be compromised if the attacker gained access + to the plaintext and ciphertext forms of the same message. And a message could be decrypted without the key + by recognizing repeated patterns in the ciphertext representing common words. More advanced symmetric + encryption methods--like the Advanced Encryption Standard (AES) algorithm, developed for the US National + Institute of Standards and Technologies--disrupt patterns in the message to prevent these types of attacks. +

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Symmetric encryption is an imperfect solution in the internet age. Because it requires both parties to know + the same secret key, those parties must have a secure form of communication already established. In the days + of Caesar, this key exchange could be performed confidentially by two individuals in close proximity. When + encryption is used on the internet, it cannot be assumed that the communicating parties will have had any + physical interactions--and it would be impractical to expect every new customer of an online banking service + to perform a physical key exchange. Asymmetric encryption solves this problem by removing the key exchange. + Instead of encrypting and decrypting a message with the same key, an asymmetric encryption algorithm has a + keypair, comprising a public key, used for encrypting a message, and a private key, used for decrypting a + message. The keys are so named because the private key is never shared, while the public key can be + broadcast widely.

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Typically, it demands more processing power to encrypt and decrypt messages with an asymmetric encryption + implementation than a comparable symmetric one. For this reason, it is desirable to use symmetric encryption + for most communications. An asymmetric implementation such as the Rivest--Shamir--Adleman (RSA) system is + used to perform the key exchange. One of the devices will broadcast its public RSA key to the other, which + will respond by generating an AES key, encrypting it with that RSA key, and returning it. This method of key + exchange is secure, even if every network packet is intercepted. Once the devices share an AES key, they can + communicate with the more efficient symmetric encryption method.

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