What is The Data Encryption Standard (DES)?

Instructor: Sally Cornett

Sally has a BS in computer science and over 10 years of engineering and business experience.

The Data Encryption Standard (DES) is a pioneering encryption algorithm that helped revolutionize encryption. In this lesson, we'll come to understand the current and historic significance of the Data Encryption Standard, and look at two basic encryption methods.

The Need for Encryption

The need for encryption (a way to keep information secret as it is transmitted from one source to another) long preceded the computer and technology era. Possibly the first need to encrypt data arose in times of war when military leaders needed to send orders to soldiers in the field. They certainly wanted to ensure those communications, if intercepted, could not be understood by the enemy. A famous example of this was the use of the Navajo Native American language as an encryption tool during World War II. Bilingual code-talkers were able to successfully keep US military operations in the Pacific basin secret using the Navajo language to encrypt radio communications. In modern times, we have the same basic need to secure information in transit. It is probably safe to say that most people expect their financial or health information to remain private when any part of it is transmitted electronically.

History of the Data Encryption Standard (DES)

The Data Encryption Standard (DES) is an encryption algorithm (a sequence of computerized steps required to complete a task) designed at IBM in the 1970s and approved by the US government in 1977 for encryption of sensitive but unclassified government data. It was also used early on to secure electronic fund transfers processed by banks that were members of the Federal Reserve System. Because the US government deemed this encryption method robust enough to secure sensitive data, most businesses followed suit and adopted this standard for encryption. In 1998, 21 years later, in a test to challenge the strength of the DES encryption algorithm, a computer was able to decrypt a DES encoded message in 56 hours. A year later, a network of computers was able to do the same in 22 hours. Cryptographers blame the relatively small size of the key for the lack of robustness required to allow DES to continue as a standard.

The Basics of Encryption

Information that has been encrypted is known as ciphertext. Ciphertext can only be decoded or decrypted with a key (think password). Of course, to be able to understand the encoded message, the receiver of the ciphertext must have access to the key. There are two basic encryption methods:

Symmetric Encryption

In the symmetric encryption method, both the sending system and the receiving system must have access to the same key that encrypts the transmission at the sending end and decrypts the transmission at the receiving end. If the message is to remain private, it is imperative the key be kept secret. The sender must tell the receiver what the key is in order to be able to decode the message. The need to communicate what the key is means there is always a risk that the communication containing the secret key can be intercepted. In terms of message processing, symmetric encryption is the fastest because this method does not increase the size of the encrypted message.

Asymmetric Encryption

Asymmetric encryption requires two keys: a public key that the sending system must know and a private key that only the receiving system knows. The key used to encode the message by the sending system is different than the key used by the receiving system to decode the message. The sending computer uses software to encode the message using the public key provided by the receiving system. That public key has been designed by the receiving system to work with the private key. The ciphertext encoded with the public key can only be unlocked with the private key designed to work with that public key. The receiving system is the only one with access to the private key. Since there is no need to communicate a secret key, the risk of the private key being intercepted is eliminated. Asymmetric encryption makes it easier to manage key distribution since it is okay for the public key to be known by other systems. From a performance perspective, this method increases the size of the message and therefore the time it takes to transmit the message. For large messages or large data volumes, this method is significantly less efficient.

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