Manual Pages for UNIX Darwin command on man dhparam

DHPARAM(1) OpenSSL DHPARAM(1)

NAME

dhparam - DH parameter manipulation and generation

SYNOPSIS

ooppeennssssll ddhhppaarraamm [-iinnffoorrmm DDEERR||PPEEMM] [-oouuttffoorrmm DDEERR||PPEEMM] [-iinn filename]

[-oouutt filename] [-ddssaappaarraamm] [-nnoooouutt] [-tteexxtt] [-CC] [-22] [-55] [-rraanndd

file(s)] [-eennggiinnee iidd] [numbits]

DESCRIPTION

This command is used to manipulate DH parameter files. OOPPTTIIOONNSS

-iinnffoorrmm DDEERR||PPEEMM

This specifies the input format. The DDEERR option uses an ASN1 DER

encoded form compatible with the PKCS#3 DHparameter structure. The

PEM form is the default format: it consists of the DDEERR format base64 encoded with additional header and footer lines.

-oouuttffoorrmm DDEERR||PPEEMM

This specifies the output format, the options have the same meaning

as the -iinnffoorrmm option.

-iinn filename

This specifies the input filename to read parameters from or standard input if this option is not specified.

-oouutt filename

This specifies the output filename parameters to. Standard output is used if this option is not present. The output filename should nnoott be the same as the input filename.

-ddssaappaarraamm

If this option is used, DSA rather than DH parameters are read or created; they are converted to DH format. Otherwise, "strong"

primes (such that (p-1)/2 is also prime) will be used for DH

parameter generation.

DH parameter generation with the -ddssaappaarraamm option is much faster,

and the recommended exponent length is shorter, which makes DH key

exchange more efficient. Beware that with such DSA-style DH

parameters, a fresh DH key should be created for each use to avoid

small-subgroup attacks that may be possible otherwise.

-22, -55

The generator to use, either 2 or 5. 2 is the default. If present then the input file is ignored and parameters are generated instead.

-rraanndd file(s)

a file or files containing random data used to seed the random number generator, or an EGD socket (see RANDegd(3)). Multiple

files can be specified separated by a OS-dependent character. The

separator is ;; for MS-Windows, ,, for OpenVMS, and :: for all others.

numbits this option specifies that a parameter set should be generated of size numbits. It must be the last option. If not present then a value of 512 is used. If this option is present then the input file is ignored and parameters are generated instead.

-nnoooouutt

this option inhibits the output of the encoded version of the parameters.

-tteexxtt

this option prints out the DH parameters in human readable form.

-CC this option converts the parameters into C code. The parameters can

then be loaded by calling the ggeettddhhnumbits(()) function.

-eennggiinnee iidd

specifying an engine (by it's unique iidd string) will cause rreeqq to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms. WWAARRNNIINNGGSS The program ddhhppaarraamm combines the functionality of the programs ddhh and ggeennddhh in previous versions of OpenSSL and SSLeay. The ddhh and ggeennddhh programs are retained for now but may have different purposes in future versions of OpenSSL. NNOOTTEESS PEM format DH parameters use the header and footer lines:

---BEGIN DH PARAMETERS---

---END DH PARAMETERS---

OpenSSL currently only supports the older PKCS#3 DH, not the newer

X9.42 DH. This program manipulates DH parameters not keys.

BUGS

There should be a way to generate and manipulate DH keys.