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Machine learning is a subfield of artificial intelligence (AI) concerned with algorithms that allow computers to learn. What this means, in most cases, is that an algorithm is given a set of data and infers information about the properties of the data—and that information allows it to make predictions about other data that it might see in the future. This is possible because almost all nonrandom data contains patterns, and these patterns allow the machine to generalize. In order to generalize, it trains a model with what it determines are the important aspects of the data. To understand how models come to be, consider a simple example in the otherwise complex field of email filtering. Suppose you receive a lot of spam that contains the words “online pharmacy.” As a human being, you are well equipped to recognize patterns, and you quickly determine that any message with the words “online pharmacy” is spam and should be moved directly to the trash. This is a generalization—you

The only real reason this is ever a confusing topic is because instructors spend a lot of time drilling into student’s heads that the public key is for encryption and that the private key is for decryption. In general, this is a true statement (and I’m willing to bet you’ll see it on your exam that way). However, remember that the keys are created in pairs—what one key does, the other undoes. If you encrypt something with the public key, the private key is the only one that can decrypt it. But that works in reverse, too—if you encrypt something with your private key, your public key is the only thing that can decrypt it. Keeping this in mind, the digital signature is an easy thing to understand. A digital signature is nothing more than an algorithmic output that is designed to ensure the authenticity (and integrity) of the sender—basically a hash algorithm. The way it works is simple: 1. Bob creates a text message to send to Joe. 2. Bob runs his message through a hash and gener

I know this may seem out of order, since I’ve mentioned the word “certificate” multiple times already, but it’s nearly impossible to discuss PKI without mentioning certificates, and vice versa. As you can probably tell so far, a digital certificate isn’t really involved with  encryption at all. It is, instead, a measure by which entities on a network can provide identification. A digital certificate is an electronic file that is used to verify a user’s identity, providing non-repudiation throughout the system.The certificate itself, in the PKI framework, follows a standard used worldwide. The X.509 standard, a part of a much bigger series of standards set up for directory services and such, defines what should and should not be in a digital certificate. Because of the standard, any system complying with X.509 can exchange and use digital certificates to establish authenticity. The contents of a digital certificate are listed-: Version - This identifies the certificate forma