DES
DES means Data Encryption Standard, and is an encryption block cipher defined and endorsded by the US government as an official encryption standard.
DES is a symetric cryptosystem, i.e. when used for communication both the sender and receiver must know the same secret key which is used to both encrypt ad decrypt the message. It uses a 64 bit block size, and uses a 56 bit key during encryption.
DES can also be used for single-user encryption, and enables a user to store files on a hard disc in encrypted form.
There are no known easy methods of attacking the DES algorithm; the only feasible way of breaking DES is to invest several million dollars in the computing power necessary to break it.
When using DES for communication one should change keys frequently, and pay special attention to key management. The best way of using DES for encryting files on a hard disc is not to frequently change the DES keys, as this would mean decrypting and then re-encrypting all the selected files with each key change. Instead it is better to have a master DES key which encrypts the list of DES keys used to encrypt the files.
Triple DES is an increasingly common algorithm, and means nothing more than the fact that encryption takes place three times with the DES algorithm, not just once. Greater security is given by using a different key for each of the three encryption operations.
IDEA
IDEA represents probably the best and most secure block algorithm currently available. Its popularity however seems to have been affected by the fact that it is patented (in both Europe and the US) whereas DES is not. In addition it is relatively new, having been introduced in 1992. Its popularity is increasing however, especially as it is also a part of PGP.
IDEA has a speed of encryption approximately twice that of DES. Its greater level of security when compared with DES is explained by the fact that IDEA has a key length of 128 bits. So IDEA is twice as fast as DES whilst at the same time offering over twice the level of security.
To illustrate IDEA's level of security: a brute force attack would require 228 (1038) encryptions to recover the key. To do this it would take a computer chip capable of testing a billion keys per second 1013 years to find the key.
Who can deny that IDEA is a very tough nut to crack?
Summary of symmetric encryption (private key systems):
RSA
RSA is without doubt the world's most popular public-key algorithm.
RSA Data Security Inc. developed the RSA asymmetric algorithm, for which it holds a US patent until the year 2000. RSA has become without doubt the most widely used of asymmetric algorithms, and its developers claim to have 25 million copies of its RSA technology worldwide. Many well-known names use the RSA algorithm for use in their products such as IBM, Microsoft, Lotus, Apple, Novell, AT&T, and Digital. In addition Boeing, Shell Oil, DuPont, Raytheon, and Citicorp use RSA internally.
RSA is de facto an encryption standard in much of the world, even though it hasn't gained the full recognition of the ISO. Individual countries (such as Australia) have chosen do adopt RSA as a standard, as have some sectors of industry (such as the French banking sector).
An important feature of RSA is its system of verifying digital signatures.
A digital signature:
Summary of asymmetric encryption (public key systems):
What Is An Elliptic Curve Cryptosystem (EEC)?
Elliptic Curve Cryptosystems (EEC) use the algebraic system defined on the points of an elliptic curve to provide public-key (assymetric) cryptographic algorithms which can be used to:
The RSA, ElGamal, and Diffie-Hellman key exchange schemes are based on mathematical operations with prime number fields or residue class rings. The difficulties of breaking these schemes rest upon the intractability of factorization and the problems associated with discrete logarithms. The weakness of the RSA scheme is given by the fact that by using low exponents it is easily broken in 'Hasted Attacks'.
AEC has developed a software solution that enables the practical use of the ELLIPT public-key encryption algorithm based on the Elliptic Curve Cryptosystem (ECC). ELLIPT uses encryption, digital signatures, and key management to provide high levels of security, making it the ideal choice for the most demanding environments. AEC is currently incorporating ELLIPT into its IronWare products to enable secure communication via the Internet. ECC is also a draft standard with three major standards organizations: the Institute of Electrical and Electronics Engineers (IEEE), the International Standards Organization (ISO), and the American National Standards Institute (ANSI).
ECC Mathematical History
The problem of elliptic curves over the finite field has been well-known for many years.
The use of elliptic curves in public-key systems was first proposed by Neal Koblitz at the University of Washington. The basic idea is to use the group of points (called a Galois field) on an elliptic curve and apply then to existing discrete-logarithm based systems. The security of the elliptic curve discrete logarithm problem has been studied for many years by various researchers including the following:
N. Koblitz A. Menezes, T. Okamoto and S. Vanstone V. Miller
Exhaustive studies have been unable to identify weaknesses in the method which would affect its effectiveness.
Despite the complexity of the mathematical calculations required for ECC, ELLIPT requires approximately the same time as RSA for encryption and key generation. Therefore AEC's ELLIPT offers much higher levels of security without compromising ease of use.
Why ECC has a good future
Recent improvements in integer factorization and parallel processing will result in a requirement for longer key sizes for most current public-key systems. Longer key sizes will make public-key systems even slower. Use of ECC allows increases in both key length and strength without loss of speed
Current ECC Standards