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RFC 6238 - TOTP: Time-Based One-Time Password Algorithm. Extends HOTP (RFC 4226) by using time as the moving factor instead of a counter, enabling time-synchronized OTP generation. Use when working with TOTP, time-based authentication, Google Authenticator, or OATH time-based standards.
Codex 또는 Claude로 설치 이 Prompt를 복사해 Codex, Claude 또는 다른 어시스턴트에 붙여 넣으면 Skill 페이지를 검토하고 설치를 진행할 수 있습니다.
SOC 직업 분류 기준
| name | rfc6238 |
| description | RFC 6238 - TOTP: Time-Based One-Time Password Algorithm. Extends HOTP (RFC 4226) by using time as the moving factor instead of a counter, enabling time-synchronized OTP generation. Use when working with TOTP, time-based authentication, Google Authenticator, or OATH time-based standards. |
Title: TOTP: Time-Based One-Time Password Algorithm
Authors: D. M'Raihi, S. Machani, M. Pei, J. Rydell
Published: May 2011
Category: Informational
Source: RFC 6238
RFC 6238 describes an extension of the HOTP (HMAC-Based One-Time Password) algorithm defined in RFC 4226 to support a time-based moving factor. While HOTP uses an event counter as the moving factor, TOTP replaces this with a time value derived from the current Unix time and a configurable time step.
The time-based variant provides short-lived OTP values (typically valid for 30 seconds), which are desirable for enhanced security. The algorithm maintains interoperability with HOTP and can be used across VPN access, Wi-Fi network logon, and transaction-oriented web applications.
| Aspect | Details |
|---|---|
| Algorithm | Time-Based One-Time Password (TOTP) |
| Base Algorithm | HOTP (RFC 4226) with HMAC |
| Type | Time-based (Unix timestamp) |
| Default Time Step | 30 seconds |
| Purpose | Two-factor authentication |
| Use Cases | VPN, Wi-Fi, web applications, mobile apps |
| OATH Standard | Yes |
| Relation to HOTP | Extension (replaces counter with time) |
C is replaced by a time-based value TT = (Current Unix time - T0) / X
TOTP = HOTP(K, T)
Where:
K = Shared secret key (same as HOTP)T = Number of time steps since T0X = Time step size in seconds (default: 30)T0 = Unix time to start counting (default: 0, the Unix epoch)HOTP = The algorithm from RFC 4226With default settings (X = 30 seconds, T0 = 0):
The RFC specifies these requirements:
TOTP inherits all security properties from HOTP (RFC 4226):
While HOTP (RFC 4226) specifies HMAC-SHA-1, TOTP implementations MAY use:
| Feature | HOTP (RFC 4226) | TOTP (RFC 6238) |
|---|---|---|
| Moving Factor | Event counter | Unix time |
| Validity | Until next event | Time step duration |
| Synchronization | Counter-based | Clock-based |
| Typical Use | Hardware tokens | Mobile apps, software |
| Drift Handling | Counter resync | Clock drift tolerance |
| Example | YubiKey | Google Authenticator |
Use this skill when:
Appendix A of RFC 6238 includes reference implementations and Appendix B provides test vectors for verification.
See references/RFC6238.txt for the complete document.
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