Hash Functions

• Mapping from type T to unsigned integers
• T is the key type; elements of T are called keys
• Corresponding unsigned integer called signature or hash value
• NOT one-to-one
• In theory and practice: not invertible
• Two principal uses:
• Secure signatures
• Efficient tables
• Security related to enigma attribute
• Very difficult (computationally intractable) to discover key from signature
• Table efficiency related to pseudo-random attribute
• Mapping appears not to respect any T structure