Module hotp 

HOTP (RFC 4226) — HMAC-Based One-Time Password Algorithm

Implements the HOTP algorithm as specified in RFC 4226 for counter-based one-time password generation and validation. HOTP uses a shared secret and a monotonically increasing counter to generate OTPs.

Security Considerations

• Secrets must be generated with a cryptographically secure RNG
• Counter values must never be reused (monotonically increasing)
• Look-ahead window should be kept small to limit brute-force surface
• Secrets should be stored encrypted at rest

Structs

HotpConfig

HOTP configuration.

HotpManager

HOTP manager for generating and validating counter-based OTPs.