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.\" NetBSD Foundation by Alistair Crooks (agc@NetBSD.org)
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.Dd September 9, 2010
.Dt LIBPAA 3
.Os
.Sh NAME
.Nm libpaa
.Nd Public key Access Authentication Library
.Sh LIBRARY
.Lb libpaa
.Sh SYNOPSIS
.In libpaa.h
.Ft int
.Fo paa_server_init
.Fa "paa_server_info_t *server" "unsigned secretsize"
.Fc
.Ft int
.Fo paa_format_challenge
.Fa "paa_challenge_t *challenge" "paa_server_info_t *server"
.Fa "char *buf" "size_t size"
.Fc
.Ft int
.Fo paa_format_response
.Fa "paa_response_t *response" "netpgp_t *netpgp" "char *in"
.Fa "char *out" "size_t outsize"
.Fc
.Ft int
.Fo paa_check_response
.Fa "paa_challenge_t *challenge" "paa_identity_t *id"
.Fa "netpgp_t *netpgp" "char *response"
.Fc
.Ft int
.Fo paa_print_identity
.Fa "FILE *fp" "paa_identity_t *id"
.Fc
.Sh DESCRIPTION
.Nm
is a library interface which provides an authentication mechanism
layered on top of
.Xr libnetpgp 3 .
This is targeted at web services, and allows authentication by
means of digitally signing a generated challenge.
By verifying the signed response from the client, the server
can verify the identity of the user receiving the challenge,
and producing the signed response.
Random seeds and blinded secrets are used to protect against
spoofed signatures.
.Pp
The main reason for writing this authentication mechanism is
so that identities can be verified across a network without
transferring any secret information across the wire.
.Pp
Binary information is transferred using internal base64
functions.
.Pp
In the server
process, the server information is initialised using the
.Fn paa_server_init
function, which will set up the random data and secrets.
The challenge is generated using the
.Fn paa_format_challenge
function.
This will format the challenge into the buffer provided,
and can be transferred to the client using any means.
.Pp
The client reads the challenge, and produces a response
using the
.Fn paa_format_response
function to format the response in the buffer provided.
This response is given to the server.
.Pp
In the server, the response is verified using
the
.Fn paa_check_response
function.
If a positive verification has occurred, the identity of
various fields in the response can be displayed
using the
.Fn paa_print_identity
function.
.Sh SEE ALSO
.Xr libnetpgp 3 ,
.Xr sha1 3
.Sh HISTORY
The
.Nm
library first appeared in
.Nx 6.0 .
.Sh AUTHORS
.An Alistair Crooks Aq Mt agc@NetBSD.org