![](https://csdnimg.cn/release/download_crawler_static/2512228/bg6.jpg)
• public key (REQUIRED)
• password (OPTIONAL)
• hostbased (OPTIONAL)
• none (NOT RECOMMENDED)
Additional authentication methods can be defined. The naming must conform
to SSH–ARCH [YL05b] and SSH–NUMBERS [LL05].
If the server rejects the authentication request, it responds with the following:
byte SSH_MSG_USERAUTH_FAILURE
name-list authentications that can continue
boolean partial success
The “authentications that can continue” is a comma–separated name–list of
authentication “method name” values that may productively continue the au-
thentication dialog.
When the server accepts authentication, it responds with the following:
byte SSH_MSG_USERAUTH_SUCCESS
Note that this is not sent after each step in a multi–method authentication
sequence, but only when the authentication is complete.
2 User authentication method “zk”
2.1 The Ohta-Okamoto Zero-Knowledge Identification Pro-
tocol
The zero-knowledge protocol used by the zk-ssh project is due to Ohta and
Okamoto [OO88]. It is a modification and generalization of the well-known
Fiat-Shamir scheme [FS86], but has one crucial advantage: It is, to the best of
our knowledge, not e ncumbered by patents.
Ohta and Okatomo present a sequential version in some detail, and discuss the
security of a parallel scheme, but they do not present the parallel protocol’s
actions. Therefore, we will do this ourselves.
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