Symmetric And Asymmetric Encryption Algorithms

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Symmetric and Asymmetric Encryption Algorithms

Symmetric and Asymmetric Encryption Algorithms


A symmetric encryption algorithm is a cryptosystem which is in contrast to an asymmetric encryption algorithm. A symmetric encryption algorithm uses the same cryptographic key both the encryption of information as for decrypting it. Such keys are mentioned symmetric keys. An example of a symmetric key is a session key. Some examples of symmetric encryption algorithms are AES, S-DES, IDEA, and RC4. Asymmetric encryption is a technique in cryptography that involves using two different keys: one open for others to encrypt and with its own private to decrypt. These keys are mathematically related in a way that it would take a long time to find it private if you have access to open. Theoretically, there is nothing to prevent this, but in practice it may be impossible for lack of time. Few examples of asymmetric encryption algorithms are: Diffie-Hellman, RSA, DSA, and Merkle-Hellman.

Comparison of Symmetric Algorithms with Asymmetric Algorithms

In Symmetric cryptosystem, both participants use the same key. Some symmetric algorithms (such as IDEA) are the two keys are not identical, but they can be calculated apart. Public-key cryptography is asymmetric encryption, where the keys are not used in the calculations because of the difficulty in practice can be deduced from each other. Thus, only one of the keys to the need to keep private, while the other may be published. Public-key encryption algorithms - for example, RSA - are widely used in asymmetric encryption format, resulting in "asymmetrical" and "public key encryption" is used largely synonyms ways (Stallings, 2006).

The big disadvantage of symmetric methods is the use of one and the same key for encryption and decryption, i.e. in addition to the encrypted information must also be communicated to the key. The problem with using symmetric procedures that the key is transmitted over a secure channel is required, because the reliability of the method depends on the secrecy of the key. Previously the key is typically delivered personally by a messenger. Since the 1970s, are the Diffie-Hellman key exchange asymmetric key exchange protocols known which can also intercepted a channel key is securely transmitted. Another way to use asymmetric encryption method to the symmetric key to encrypt itself and protected him so transmitted over an insecure channel. When communicating with you this hybrid encryption so the benefits (for example, the higher speed) can be exploited symmetric encryption, while the key is protected by asymmetric encryption before accessing an attacker (Forouzan, 2007).


Speed (according to Applied Cryptography - 3 orders of magnitude higher)

Ease of implementation (due to its simple operation)

Less than the required length of the key for a comparable strength

Study (due to the greater age)


The complexity of key management in a large network. Mean quadratic increase in the number of key pairs that need to generate, transmit, store and destroy the network. For a network of 10 users required 45 keys for 100 already 4950, for 1000 - 499,500, etc.

The complexity of key exchange. For the application to solve the problem of reliable transmission ...
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