<del> HTTP Unprompted Authentication </del> <ins> The Signature HTTP Authentication Scheme </ins> draft-ietf-httpbis-unprompted-auth-latest Abstract <del> Existing HTTP authentication mechanisms are probeable in the sense that it is possible for an unauthenticated client to probe whether an </del> <ins> Existing HTTP authentication schemes are probeable in the sense that it is possible for an unauthenticated client to probe whether an </ins> origin serves resources that require authentication.  It is possible for an origin to hide the fact that it requires authentication by not generating Unauthorized status codes, however that only works with <del> non-cryptographic authentication schemes: cryptographic schemes (such as signatures or message authentication codes) require a fresh nonce to be signed, and there is no existing way for the origin to share such a nonce without exposing the fact that it serves resources that require authentication.  This document proposes a new non-probeable cryptographic authentication scheme. </del> <ins> non-cryptographic authentication schemes: cryptographic signatures require a fresh nonce to be signed, and there is no existing way for the origin to share such a nonce without exposing the fact that it serves resources that require authentication.  This document proposes a new non-probeable cryptographic authentication scheme. </ins> 1. <del> Existing HTTP authentication mechanisms (see HTTP) are probeable in the sense that it is possible for an unauthenticated client to probe </del> <ins> Existing HTTP authentication schemes (see HTTP) are probeable in the sense that it is possible for an unauthenticated client to probe </ins> whether an origin serves resources that require authentication.  It is possible for an origin to hide the fact that it requires authentication by not generating Unauthorized status codes, however that only works with non-cryptographic authentication schemes: <del> cryptographic schemes (such as signatures or message authentication codes) require a fresh nonce to be signed, and there is no existing way for the origin to share such a nonce without exposing the fact that it serves resources that require authentication.  This document proposes a new non-probeable cryptographic authentication scheme. Unprompted Authentication serves use cases in which a site wants to offer a service or capability only to "those who know" while all others are given no indication the service or capability exists.  The conceptual model is that of a "speakeasy".  "Knowing" is via an externally-defined mechanism by which keys are distributed.  For example, a company might offer remote employee access to company </del> <ins> cryptographic signatures require a fresh nonce to be signed, and there is no existing way for the origin to share such a nonce without exposing the fact that it serves resources that require authentication.  This document proposes a new non-probeable cryptographic authentication scheme. The Signature HTTP authentication scheme serves use cases in which a site wants to offer a service or capability only to "those who know" while all others are given no indication the service or capability exists.  The conceptual model is that of a "speakeasy".  "Knowing" is via an externally-defined mechanism by which keys are distributed. For example, a company might offer remote employee access to company </ins> services directly via its website using their employee credentials, or offer access to limited special capabilities for specific employees, while making discovering (probing for) such capabilities