What is Asymmetric Cryptography?
Asymmetric cryptography also uses mathematical permutations to encrypt a plain text message, but it uses two different permutations, still known as keys, to encrypt and decrypt messages. With asymmetric cryptography, a public key that can be shared with anyone gets used to encrypt messages while a private key that’s known only by the recipient gets used to decrypt messages.
Critically, it should be relatively easy to compute the public key from the private key but nearly impossible to do the reverse and generate the private key from the public key. Three popular mathematical permutations, known asRSA, ECC and Diffie-Hellman, accomplish this today. Each uses different algorithms but they all rely on the same basic principles. For instance, the RSA 2048 bit algorithm randomly generates two prime numbers that are each 1024 bits long and then multiplies them together. The answer to that equation is the public key, while the two prime numbers that created the answer are the private key.
How exactly does this all work? Let’s say Alice wants to send a private message to Bob. Bob can share his public key with Alice, which she then uses to encrypt her message. Once the message gets encrypted, only Bob’s private key can decrypt it. This means that as long as Bob ensures no one else has his private key, then no one can read the encrypted message
The above example offers a more secure way to encrypt messages compared to symmetric cryptography; however, asymmetric cryptography also powers additional, more advanced use cases.
Consider digital signatures. In this case, Bob might want to send a message to Alice and add a digital signature so she can verify it was in fact Bob who sent it. He can do so by encrypting a signature using his private key. When Alice receives the message, she can use Bob’s public key to verify that Bob (or someone with Bob’s private key) sent the message and that the message was not modified in transit (because if it does get modified, the verification will fail).
It’s important to note that all of these examples are one-way. To reverse any of them (e.g. so Bob can send private messages to Alice and Alice can send messages to Bob that contain her digital signature), Alice needs her own private key and must share the corresponding public key with Bob.
