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.\" Author: Archie Cobbs <archie@freebsd.org>
.\"
.\" $Id: rsa_util_sign.3,v 1.1.1.1 2012/02/21 23:25:53 misho Exp $
.\"
.Dd April 22, 2002
.Dt RSA_UTIL_SIGN 3
.Os
.Sh NAME
.Nm rsa_util_sign ,
.Nm rsa_util_verify ,
.Nm rsa_util_verify_priv
.Nd RSA digital signature routines
.Sh LIBRARY
PDEL Library (libpdel, \-lpdel)
.Sh SYNOPSIS
.In sys/types.h
.In pdel/util/rsa_util.h
.Ft int
.Fn rsa_util_sign "const char *privkeyfile" "const u_char *md5" "u_char *sig" "size_t siglen"
.Ft int
.Fn rsa_util_verify "const char *pubkeyfile" "const u_char *md5" "const u_char *sig" "size_t siglen"
.Ft int
.Fn rsa_util_verify_priv "const char *privkeyfile" "const u_char *md5" "const u_char *sig" "size_t siglen"
.Sh DESCRIPTION
These routines are convenience wrappers around the OpenSSL crypto library
for creating and verifying RSA digital signatures.
They use the
.Xr md5 3
hash of the original document for the actual signing operation.
.Pp
.Fn rsa_util_sign
creates a digital signature.
.Fa privkeyfile
is the pathname of the private key file (which must be unencrypted).
.Fa md5
is the hash of the document to be signed.
.Fa sig
points to a buffer of at least 128 bytes.
.Fa siglen
is the size of the buffer.
.Fn rsa_util_sign
returns the length of the resulting signature, or -1 (with
.Va errno
set) if there was an error.
.Pp
.Fn rsa_util_verify
verifies a digital signature.
.Fa pubkeyfile
is the pathname of the public key file.
.Fa md5
is the hash of the document to be signed.
.Fa sig
points to the signature to verify, having length
.Fa siglen .
.Fn rsa_util_verify
returns 1 if the signature is valid, otherwise 0.
.Pp
.Fn rsa_util_verify_priv
functions exactly like
.Fn rsa_util_verify
except that the private key file (which also contains the public key)
is passed as the first argument.
.Sh EXAMPLES
To create a new RSA private key:
.Bd -literal -offset 3n
openssl genrsa -rand /dev/random -out mykey.key 1024

.Ed
To view the contents of an RSA private key file:
.Bd -literal -offset 3n
openssl rsa -in mykey.key -text -noout

.Ed
To extract the RSA public key from an RSA private key file:
.Bd -literal -offset 3n
openssl rsa -in mykey.key -pubout -out mykey.pub

.Ed
To view the contents of an RSA public key file:
.Bd -literal -offset 3n
openssl rsa -pubin -in mykey.pub -text -noout
.Ed
.Sh SEE ALSO
.Xr openssl 1 ,
.Xr md5 3 ,
.Xr libpdel 3
.Sh HISTORY
The PDEL library was developed at Packet Design, LLC.
.Dv "http://www.packetdesign.com/"
.Sh AUTHORS
.An Archie Cobbs Aq archie@freebsd.org