code: 9ferno

ref: 44ce0097b612a1fefd754065bdf8d9d2e5ef60c8
dir: /man/2/crypt-0intro/

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.TH CRYPT-INTRO 2
.SH NAME
Crypt intro \- introduction to the
.B Crypt
cryptography
module
.SH SYNOPSIS
.EX
include "ipints.m";
ipints := load IPints IPints->PATH;
IPint: import ipints;

include "crypt.m";
crypt := load Crypt Crypt->PATH;
.EE
.SH DESCRIPTION
.B Crypt
contains a mixed set of functions that variously:
.IP \(bu
form cryptographically secure digests; see
.IR crypt-sha1 (2)
.IP \(bu
generate public/private key pairs; see
.IR crypt-gensk (2)
.IP \(bu
encrypt data, using AES, DES, or IDEA; see
.IR crypt-crypt (2)
.IP \(bu
create and verify cryptographic signatures using the
public keys; see
.IR crypt-sign (2)
.SS "Public Key Cryptography"
Public key cryptography has many uses.
Inferno relies on it only for digital signatures.
The private key may be used to digitally
sign data, the public one to verify the signature.
.PP
Inferno provides three data types to represent the different components of the public key signature scheme.
The
.B PK
adt contains the data necessary to construct a public key;
the
.B SK
adt contains the data necessary to construct a secret key.
A key contains the public or secret parameters for the signature algorithm specified by the adt's pick tag.
Ownership of a key is not recorded in the key value itself but in a separate certificate.
Finally,
the
.B PKsig
adt contains one or more values representing a given form of digital signature.
.PP
Certificates and indeed signature representations are varied, and implemented by other modules.
.SS "Large Precision Arithmetic"
Many
.B Crypt
operations require integers much larger than
.B int
or
.BR big .
It therefore uses the multiple-precision package
.IR ipints (2).
That module's
.B IPint
adt
stands for infinite precision integer, though, for
space considerations, our
implementation limits the maximum integer to
2\u\s-2\&8192\s0\d-1.
.PP
An
.B IPint
can be converted into two external formats.
The first is
an array of bytes in which the first byte is the highest order
byte of the integer.  This format is useful when
communicating with the
.IR ssl (3)
device.
The second is similar but represents the array of bytes as text, using either base 16 or a MIME base 64 format,
allowing
.BR IPint s
to be stored in files or transmitted across
networks in a human readable form.
.SH SOURCE
.br
.B /libinterp/crypt.c
.br
.B /libinterp/ipint.c
.br
.B /libmp
.br
.B /libsec
.SH SEE ALSO
.IR security-intro (2)
.br
B. Schneier,
.IR "Applied Cryptography" ,
1996, J. Wiley & Sons, Inc.