IPSec Anti-Replay Window Circular Buffer Index Update

Solution Overview

Problem

Existing anti-replay window mechanisms in IPSec protocols are inefficient due to frequent bit-shifting operations, especially with large window sizes, which consume power and time, and are not optimized for high-speed applications.

Innovation Solution

Implementing a circular buffer with redundant bits to update the anti-replay window by incrementing low and high indices without bit-shifting, allowing the window to wrap around, thereby reducing the frequency of updates and simplifying the authentication process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If bit-shifting operations are used to update the anti-replay window, then the window can be efficiently updated, but processing time and power consumption increase significantly

Engineering Contradiction:

Improveanti-replay window update efficiencyVSAvoidprocessing time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent replaces the mechanical bit-shifting operation with a simpler index incrementing mechanism. Instead of physically shifting bits in a circular buffer, the system increments integer indices (low_index and high_index) to track the window position, substituting complex bit manipulation with simpler arithmetic operations that are faster and less power-consuming.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the representation parameter from bit-level shifting to index-level incrementing. By maintaining the anti-replay window as a circular buffer with integer indices rather than performing bit shifts, the system achieves the same functional result (window advancement) through a more efficient parameter manipulation approach.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If bit-shifting operations are used to update the anti-replay window, then the window can be efficiently updated, but power consumption increases significantly

Engineering Contradiction:

Improveanti-replay window update efficiencyVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the mechanical bit-shifting operation with a simpler index incrementing mechanism. Instead of physically shifting bits in a circular buffer, the system increments integer indices (low_index and high_index) to track the window position, substituting complex bit manipulation with simpler arithmetic operations that are faster and less power-consuming.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the representation parameter from bit-level shifting to index-level incrementing. By maintaining the anti-replay window as a circular buffer with integer indices rather than performing bit shifts, the system achieves the same functional result (window advancement) through a more efficient parameter manipulation approach.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If frequent window updates are performed, then the anti-replay mechanism remains current, but processing overhead increases

Engineering Contradiction:

Improveanti-replay mechanism effectivenessVSAvoidprocessing overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies partial action by updating the window indices only when necessary (when the received sequence number exceeds the high_index). This selective updating approach maintains anti-replay effectiveness while reducing unnecessary processing overhead that would occur with continuous or frequent updates.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the update mechanism from frequent bit-shifting operations to occasional index incrementing. By using integer index arithmetic that can handle larger jumps (when multiple packets arrive in sequence), the system reduces the frequency of updates while maintaining the same reliability in detecting replay attacks.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8943578B2Method and apparatus for fast check and update of anti-replay window without bit-shifting in internet protocol security

Publication Date: 2015.01.27 FUTUREWEI TECHNOLOGIES INC

AI summary

An apparatus comprising a processor configured to implement an anti-replay check for a plurality of received packets and a plurality of corresponding sequence numbers; and a circular buffer coupled to the processor and comprising a bitmap, wherein the bitmap is slided in a circular manner by updating a low index that points to a first sequence number for a first received packet and a high index that points to a last sequence number for a last received packet without bit-shifting, and wherein, when the update results in the new value of one of the low index and the high index exceeding the end of the circular buffer, the one of the low index and the high index wraps around from the beginning of the circular buffer.