Performance vs Security

CPU Overhead

The amount of time it takes to encrypt and decrypt text using the key as well as the time it takes to authenticate each packet and each user. Key Length and Encryption Method are the two biggest factors.

Depending on the Encryption method, the minimum safe key length will vary. As technology continues, longer minimum key lengths will be required to maintain the same safety level.

Here too, depending on both the Encryption method and possibly the Key Length, will determine how much additional bandwidth is required. Also, depending on whether you are using transport or tunnel mode will cause a difference in required bandwidth. Transport only requires the encryption overhead alone while tunnel requires that the original IP header be encapsulated and encrypted with the data requiring a new external IP header to be added increasing the required bandwidth.

RSA: To decrease the Encryption/decryption overhead and authentication time, shorter keys are preferred, but the breach security threat increases proportionally as well. To decrease bandwidth, encryption more along the lines of ECC is preferred as the encrypted size is smaller than that required for RSA.

ECC: The CPU overhead is much smaller than RSA (by a factor of about 1:10), bandwidth utilization is also much better than RSA.

At present, the NSA is currently placing much emphasis on diasecting and performing numerous ECC tests as the possible next NSA encryption method of choice, but very few vendors currently support this method, thus compatibility will remain a concern until ECC becomes the preferred encryption method of choice.

New ideas and proposals are constantly being drafted, so this could become a never ending story!!!