Advantages and Disadvantages of Symmetrical and Asymmetrical Encryption

By Milton Kazmeyer

Different forms of encryption offer different advantages.
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While there are many different encryption schemes available, most fall into one of two categories, symmetric or asymmetric. Symmetric encryption methods involve a single key, which you use to both encode and decode data. Asymmetric schemes involve a linked pair of keys, public and private, and anything encoded by one requires the other to decode. Each method has its advantages and disadvantages, and knowing the strengths of each method can help you protect vital data.

Ease of Use

For simple encryption, such as encrypting the files on your hard drive, a symmetric system should suit your needs. Symmetric encryption only requires you to maintain and remember a single key and only requires a single decryption step to return your data to a readable format. If you have a secure method of communicating a symmetric key to multiple users, you can also use a symmetric encryption system to share data across a network. The same key will allow any authorized user access to the hidden content.

Internet Correspondence

Encryption can keep your emails secure, but you face a dilemma when contacting someone new. If you use a symmetric encryption system, you have to send the key, but that may allow an outsider to intercept the email and render your encryption useless. Asymmetric encryption gets around this by allowing users to exchange public keys. Since the public key cannot decode public key-encrypted messages, two users can communicate using encryption unique to their conversation. This type of transfer also lies at the heart of SSL, when your browser encrypts a symmetric key using the server’s public key, ensuring that no one can steal the key in transit.

Identification and Verification

Another advantage of asymmetric encryption is its ability to serve as identification. If you encode a known string of data with your private key and attach it to a message, anyone who receives that message can decode it with your public key. Therefore, the encryption serves as a fingerprint, since only your private key could have encrypted the data. Another technique involves running a document through a hash function, a one-way cryptographic encoding that produces a unique result for each input. By hashing a message and encoding the hash using your private key, you not only prove your identity to the recipient, but you also ensure that no one was able to tamper with the message, since the hash would change.

Digital Registry

To get full use of asymmetric encryption, you have to provide access to your public key. For private correspondence, simply appending the key to your email or message board signature might suffice, but companies that wish to use asymmetric encryption to transact business must go a step further. A digital certificate provides a record of your company or server information as well as your public key for anyone to access, allowing your identity to be verified. These services cost money, however, and you must keep your certificate current to take advantage of SSL and other protocols that encrypt data transfers.