What is Timing Attack?
A side-channel attack where an adversary measures microsecond variations in computation or comparison execution time to infer secret cryptographic keys, passwords, or authentication tokens.
Execution Time as an Information Leak
In non-hardened software, operations take varying amounts of time depending on the input data. For example, standard string comparison algorithms (like C's strcmp or JavaScript's ===) terminate immediately upon finding the first mismatched character.
An attacker who can measure server response times with microsecond precision can systematically guess passwords or HMAC webhook signatures character-by-character: an input whose first character is correct takes slightly longer to reject than an input with an incorrect first character.
Constant-Time Equality Algorithms
To prevent timing leaks, cryptographic routines must execute in constant time, meaning execution duration is completely independent of whether data matches or where mismatches occur.
DocSwift implements constant-time verification using bitwise XOR accumulation (`diff |= a[i] ^ b[i]`) across all bytes, ensuring identical CPU cycle counts and eliminating timing side-channels.
Key Advantages & Impact
- Eliminates subtle side-channel leaks that bypass standard network encryption
- Mandatory standard for verifying webhook signatures, JWT tokens, and API authentication secrets
- Independent of computational power: constant-time algorithms resist brute-force parallelization
Common Misconceptions vs Reality
Experience This Technology in DocSwift Tools
Frequently Asked Questions
How does DocSwift protect webhook verification against timing attacks?
DocSwift Webhook Verifier uses constant-time byte-by-byte comparisons in WebAssembly/Web Crypto, ensuring execution time never leaks secret information.