Use of Symmetric Encryption

Symmetric encryption isn’t only the most conventional type of encryption, but it’s also the most used type of encryption today, especially for protecting bulk data. Indeed, its prevalence over public-key encryption is so ubiquitous that if someone mentions ‘encryption’ without specifying the type, then they usually mean ‘symmetric encryption.’ We’ll also discover that even when public key encryption is used, it tends to be employed alongside symmetric encryption.

Other types of symmetric encryption

There are a couple of extensions to the basic idea of symmetric encryption worthy of mention. These are not yet common but have clear applications that will likely see wider adoption.

• Searchable encryption: It’s a natural requirement to encrypt entries in a database. However, one of the most fundamental requirements of a database is that it should be searchable. Suppose the data in the database is encrypted. In such a case, searching the database essentially requires the database to be decrypted before the search can be conducted (since the stored ciphertext itself should not reveal information about the underlying plaintext). This is somewhat inefficient. More problematically, if the platform on which the encrypted database is held isn’t fully trusted, then this necessary decryption process is highly undesirable.

  Indeed, in such a situation, even the search queries and results themselves may be sensitive since they can leak information about the underlying content. Searchable encryption is designed to address this issue by encrypting data alongside special indices, facilitating limited search capability. These indices typically represent searchable keywords associated with the data. Some searchable encryption schemes have been proposed that vary in the form of search queries they permit and the degree of protection they provide for the privacy of queries.