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Cryptography Algorithms: The 3 types

CISSP, GIAC GSEC, Security+ Review

There are three types or "flavors" of cryptoalgorithms and cryptography:

With symmetric key cryptography, there is one key, and it's used to both encrypt and decrypt data. This is often called the "secret key" as the two parties using symmetric key need to keep this secret. Anyone who has this secret key can encrypt and decrypt data.

With asymmetric key cryptography, each entity has two keys, a public key and a private key. Anything encrypted by the public key can only be decrypted by the private key and anything encrypted by the private key can only be decrypted by the public key.

For example, if you want to send an encrypted message to someone using asymmetric key, you use their public key to encrypt it. Their public key is "public knowledge" and may be stored in a directory, perhaps in a digital certificate. To decrypt the message, the associated private key is needed. Assuming the private key has been kept private, only the intended recipient has it and can decrypt the message.

Hashing algorithms, also known as "message digests," perform one-way encryption. Hashing algorithms are not used for confidentiality, but for integrity. A hash value is link a fingerprint. If the data has changed at all, even one bit, the hash value differs and we know it's been modified