| Public Key Cryptography |
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| Public Key Cryptography |
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Recall from earlier that public key encryption is any form of cryptography where the process and/or key used to encrypt data is fundamentally different from the process and/or key used to decrypt data. At the heart of this kind of encryption is a mathematical property known as asymmetry. Following is a simple equation:
X + 7 = 10
We can quickly determine that X must be equal to 3. This equation is fully reversible and is therefore symmetric. However, looking at this next equation:
X^2 = 4
We cannot be certain what the value of X actually is. Is it 2, or 2? It's impossible to tell for certain, but at least the number of possible answers is few. This equation is partially reversible and therefore partially symmetric. Now consider the modulus operation:
X mod 7 = 3
Given this equation there are literally an infinite number of possible values for X: 3, 10, 17, 24, 31, 38, and so on. Each one of these numbers, when divided by 7, yields a remainder of 3. Because it's impossible to make even a probable guess at the value of X, this equation is considered nonreversible and fully asymmetric.
The RSA Algorithm
By far the most popular algorithm to take advantage of this property of asymmetric equations is the RSA algorithm. RSA was named for the first letter in the last names of its inventors: Ron Rivest, Adi Shamir, and Leonard Adleman. The RSA algorithm amplifies the indeterminacy of asymmetric equations by pairing them with very large numbers and provides a "backdoor" to decode this nonreversible equation through a fortunate side-effect of the very thing that makes the equation nonreversible in the first place.
At the core of RSA is a deceptively simple equation:
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