NAME¶
genrsa - generate an RSA private key
SYNOPSIS¶
openssl genrsa [
-out filename] [
-passout arg] [
-des] [
-des3] [
-idea] [
-f4] [
-3] [
-rand file(s)] [
-engine id] [
numbits]
DESCRIPTION¶
The
genrsa command generates an RSA private key.
OPTIONS¶
- -out filename
- the output filename. If this argument is not specified then
standard output is used.
- -passout arg
- the output file password source. For more information about
the format of arg see the PASS PHRASE ARGUMENTS section in
openssl(1).
- -des|-des3|-idea
- These options encrypt the private key with the DES, triple
DES, or the IDEA ciphers respectively before outputting it. If none of
these options is specified no encryption is used. If encryption is used a
pass phrase is prompted for if it is not supplied via the -passout
argument.
- -F4|-3
- the public exponent to use, either 65537 or 3. The default
is 65537.
- -rand file(s)
- a file or files containing random data used to seed the
random number generator, or an EGD socket (see RAND_egd(3)).
Multiple files can be specified separated by a OS-dependent character. The
separator is ; for MS-Windows, , for OpenVMS, and :
for all others.
- -engine id
- specifying an engine (by its unique id string) will
cause genrsa 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.
- numbits
- the size of the private key to generate in bits. This must
be the last option specified. The default is 512.
NOTES¶
RSA private key generation essentially involves the generation of two prime
numbers. When generating a private key various symbols will be output to
indicate the progress of the generation. A
. represents each number
which has passed an initial sieve test,
+ means a number has passed a
single round of the Miller-Rabin primality test. A newline means that the
number has passed all the prime tests (the actual number depends on the key
size).
Because key generation is a random process the time taken to generate a key may
vary somewhat.
BUGS¶
A quirk of the prime generation algorithm is that it cannot generate small
primes. Therefore the number of bits should not be less that 64. For typical
private keys this will not matter because for security reasons they will be
much larger (typically 1024 bits).
SEE ALSO¶
gendsa(1)