Symmetric Key Algorithms + Asymmetric Key Algorithms + Key Escrow + Hash Functions

Symmetric key cryptography has several weaknesses

• Key exchange is a major problem

• Symmetric key cryptography does not implement non-repudiation

• The algorithm is not scalable

• Keys must be regenerated often

The major strength of symmetric key cryptography

is the great speed at which it can operate

The following is a list of the major strengths of asymmetric key cryptography

• The addition of new users requires the generation of only one public-private key pair (2 keys)

• Users can be removed far more easily from asymmetric systems

• Key regeneration is required only when a user’s private key is compromised

• Asymmetric key encryption can provide integrity, authentication, and non-repudiation

• Key exchange is a simple process

• No preexisiting communication link needs to exist

The major weakness of public key (asymmetric) cryptography

is its slow speed of operation

Key escrow

systems have a third party store a protected copy of the key for use in an emergency

There are five basic requirements for a cryptographic hash function

• They accept an input of any length

• They provide an output of a fixed length, regardless of the length of the input

• The hash value is relatively easy to compute

• The hash function is one-way (meaning that it is extremely hard to find two messages that produce the same hash value)

• A secure hash value is collision free (meaning that it is extremely hard to find two messages that produce the same hash value)