hashcash ☆
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Description:
Proof-of-work algorithm to counter denial-of-service (DoS) attacks
Type: Formula  |  Tracked Since: Dec 28, 2025
Links: Homepage  |  formulae.brew.sh
Category: Security
Tags: proof-of-work spam security dos cryptography
Install: brew install hashcash
About:
Hashcash is a proof-of-work system designed to limit email spam and denial-of-service attacks. It requires the sender to compute a cryptographic hash that meets a specific difficulty criterion before a message is accepted. This computational cost makes large-scale abuse economically infeasible for attackers.
Key Features:
  • Implements the hashcash proof-of-work algorithm
  • Command-line tool for generating and verifying stamps
  • Configurable difficulty (bits) for varying security levels
  • Supports email and general-purpose resource protection
Use Cases:
  • Rate-limiting email senders to combat spam
  • Protecting APIs or services from denial-of-service attacks
  • Preventing resource exhaustion in distributed systems
Alternatives:
  • scrypt – Memory-hard key derivation function, stronger for password hashing but more resource-intensive than hashcash's CPU-bound approach.
  • bcrypt – Adaptive hashing function primarily for passwords, not designed for lightweight, high-volume request stamping.
Version History
Detected Version Rev Change Commit
Apr 26, 2026 3:22pm 2 REVISION_ONLY b578f666
Sep 12, 2025 2:49pm 1 VERSION_BUMP e65beed0
Sep 13, 2024 4:21pm 1 VERSION_BUMP 154519a9
Aug 1, 2024 4:11pm 1 VERSION_BUMP 1c1e8957
Feb 9, 2024 3:59pm 1 VERSION_BUMP 776f09a2
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