Asymmetric cryptography is a type of encryption where the key used to encrypt the information is not the same as the key used to decrypt the information. This format is the opposite of symmetric cryptography, where the same key is used to both encrypt and decrypt the information. The most common form of asymmetric cryptography is public key encryption. While asymmetric cryptography is generally more secure that symmetric, it is also more difficult to set up and practically impossible to perform without computer assistance.
Public key encryption is by far the most common type of asymmetric cryptography. In this system, each user has two keys, a public key and a private key. The public key is published and available to any person that wants to see it. The private key is mathematically related to the public key, but the algorithm is so complex and variable that there is no reasonable way to derive a private key from a public.
Suppose a message needs to be sent from one person to another. The sender would locate the receiver’s public key and use it to encrypt a message. When the receiver gets the message, he attempts to open it. The receiver’s public key verifies that the private key is authentic. The private key then allows the user to decrypt the message and read it.
The main advantage of asymmetric cryptography is in individual security. The two people that exchange the message may never have met face-to-face; in fact, they don’t even need to know who the other person is. Since the individuals may publish their keys under any identity that they wish, there is total anonymity in the system.
This is in direct opposition to symmetric cryptography where the same key is used for encryption and decryption. In this case, it is practically impossible to not know the person deciphering a message, as the key would need to be exchanged beforehand. In an asymmetric system, it is easy to keep a key secure, but symmetric systems potentially have many people with the same key, increasing the risk it will be compromised.
One of the biggest drawbacks to asymmetric cryptography is its dependence on computers. Without a computer system, it is practically impossible to perform asymmetric encryption or decryption. Since the entire process is computer-controlled, it is also possible to break the system with a computer. While some public-key encryption is considered nearly crack-proof, every year a new cracking method comes out that requires new encryption countermeasures.