一、OTP

OTP即 One-Time Password。是目前广泛使用的2阶段密码验证技术，如 2-step verification

使用如下所示：

输入如下显示的6位数字：

二、规范

http://www.openauthentication.org/specification

• HOTP 【 An HMAC-Based OTP Algorithm (RFC 4226) 】

TXT HTML PDF

• TOTP【 Time-based One-time Password Algorithm (RFC 6238) 】

TXT HTML PDF

• OCRA 【 OATH Challenge/Response Algorithms Specification (RFC 6287) 】

TXT HTML PDF

三、实现

• Google Authenticator

http://code.google.com/p/google-authenticator/

• Hatter's Go Lang Implement

https://code.google.com/p/hatter-source-code/source/browse/trunk/golang/googleauth/googleauth.go

四、其它OTP

• Celf https://getclef.com/ - Two-factor authentication from the future.
• Waltz http://getwaltz.com/ - A modern account manager for the web

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• https://play.google.com/store/apps/details?id=com.google.android.apps.authenticator2
• https://support.google.com/accounts/answer/1066447?hl=en&ref_topic=2784804
• https://www.saaspass.com/Authenticator.html
• http://www.multiotp.net/