Article

A comparison of the approximate equivalent strengths of public and private key
cryptosystems is provided below

Equivalent Strengths of Asymmetric and Symmetric Keys
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|Asymmetric Key Size | Symmetric Key Size|
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|512 Bits | 64 Bits |
|1792 Bits | 112 Bits |
|2304 Bits | 128 Bits |
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A one-way hash is a function that takes a variable-length string and a message and produces a fixed-length value called a hash value. For example, if Kevin wants to send a message to Maureen and he wants to ensure the message does not get altered in an unauthorized fashion while it is being transmitted, he would calculate a hash value for the message and append it to the message itself. When Maureen receives the message, she performs the same hashing function Kevin used and then compare her result with the hash value sent with the message.

1. Brute force. Trying every possible combination of key patterns; the longer the key length, the more difficult it is to find the key with this method.

2. Known plaintext. The attacker has a copy of the plaintext corresponding to the ciphertext.

3. Chosen plaintext. Chosen plaintext is encrypted and the output ciphertext is obtained.

4. Adaptive chosen plaintext. A form of a chosen plaintext attack where the selection of the plaintext is altered according to the previous results.

5. Ciphertext only. Only the ciphertext is available.