5 openssl-genrsa - generate an RSA private key
28 [B<-writerand> I<file>]
34 =for comment ifdef engine
38 The B<genrsa> command generates an RSA private key.
46 Print out a usage message.
48 =item B<-out> I<filename>
50 Output the key to the specified file. If this argument is not specified then
51 standard output is used.
53 =item B<-passout> I<arg>
55 The output file password source. For more information about the format
56 see L<openssl(1)/Pass phrase options>.
58 =item B<-aes128>, B<-aes192>, B<-aes256>, B<-aria128>, B<-aria192>, B<-aria256>, B<-camellia128>, B<-camellia192>, B<-camellia256>, B<-des>, B<-des3>, B<-idea>
60 These options encrypt the private key with specified
61 cipher before outputting it. If none of these options is
62 specified no encryption is used. If encryption is used a pass phrase is prompted
63 for if it is not supplied via the B<-passout> argument.
67 The public exponent to use, either 65537 or 3. The default is 65537.
69 =item B<-rand> I<files>
71 The files containing random data used to seed the random number generator.
72 Multiple files can be specified separated by an OS-dependent character.
73 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
76 =item B<-writerand> I<file>
78 Writes random data to the specified I<file> upon exit.
79 This can be used with a subsequent B<-rand> flag.
81 =item B<-engine> I<id>
83 Specifying an engine (by its unique B<id> string) will cause B<genrsa>
84 to attempt to obtain a functional reference to the specified engine,
85 thus initialising it if needed. The engine will then be set as the default
86 for all available algorithms.
88 =item B<-primes> I<num>
90 Specify the number of primes to use while generating the RSA key. The B<num>
91 parameter must be a positive integer that is greater than 1 and less than 16.
92 If B<num> is greater than 2, then the generated key is called a 'multi-prime'
93 RSA key, which is defined in RFC 8017.
97 Print extra details about the operations being performed.
101 The size of the private key to generate in bits. This must be the last option
102 specified. The default is 2048 and values less than 512 are not allowed.
108 RSA private key generation essentially involves the generation of two or more
109 prime numbers. When generating a private key various symbols will be output to
110 indicate the progress of the generation. A B<.> represents each number which
111 has passed an initial sieve test, B<+> means a number has passed a single
112 round of the Miller-Rabin primality test, B<*> means the current prime starts
113 a regenerating progress due to some failed tests. A newline means that the number
114 has passed all the prime tests (the actual number depends on the key size).
116 Because key generation is a random process the time taken to generate a key
117 may vary somewhat. But in general, more primes lead to less generation time
127 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
129 Licensed under the Apache License 2.0 (the "License"). You may not use
130 this file except in compliance with the License. You can obtain a copy
131 in the file LICENSE in the source distribution or at
132 L<https://www.openssl.org/source/license.html>.