Security Strength of Cryptographic Algorithms

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Security strength is expressed in the total amount of computations an attacker needs to perform in order to break an algorithm (i.e. disclose a plaintext, recover the key, forge a message tag, etc.).

• aka computational complexity
• specified in number of bits
• e.g.,
  • a security strength of 256 bits means an attacker would require or more bit operations to compromise security
• security strength of a system is the minimum of the bit-lengths of its components
  • i.e. of all components have 256 bit strength but one is 128 bit, then the system has a security strength of 128 bits