1=pod 2 3=head1 NAME 4 5openssl-genrsa, 6genrsa - generate an RSA private key 7 8=head1 SYNOPSIS 9 10B<openssl> B<genrsa> 11[B<-help>] 12[B<-out filename>] 13[B<-passout arg>] 14[B<-aes128>] 15[B<-aes192>] 16[B<-aes256>] 17[B<-aria128>] 18[B<-aria192>] 19[B<-aria256>] 20[B<-camellia128>] 21[B<-camellia192>] 22[B<-camellia256>] 23[B<-des>] 24[B<-des3>] 25[B<-idea>] 26[B<-f4>] 27[B<-3>] 28[B<-rand file...>] 29[B<-writerand file>] 30[B<-engine id>] 31[B<-primes num>] 32[B<numbits>] 33 34=head1 DESCRIPTION 35 36The B<genrsa> command generates an RSA private key. 37 38=head1 OPTIONS 39 40=over 4 41 42=item B<-help> 43 44Print out a usage message. 45 46=item B<-out filename> 47 48Output the key to the specified file. If this argument is not specified then 49standard output is used. 50 51=item B<-passout arg> 52 53The output file password source. For more information about the format 54of B<arg> see L<openssl(1)/Pass Phrase Options>. 55 56=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> 57 58These options encrypt the private key with specified 59cipher before outputting it. If none of these options is 60specified no encryption is used. If encryption is used a pass phrase is prompted 61for if it is not supplied via the B<-passout> argument. 62 63=item B<-F4|-3> 64 65The public exponent to use, either 65537 or 3. The default is 65537. 66 67=item B<-rand file...> 68 69A file or files containing random data used to seed the random number 70generator. 71Multiple files can be specified separated by an OS-dependent character. 72The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 73all others. 74 75=item [B<-writerand file>] 76 77Writes random data to the specified I<file> upon exit. 78This can be used with a subsequent B<-rand> flag. 79 80=item B<-engine id> 81 82Specifying an engine (by its unique B<id> string) will cause B<genrsa> 83to attempt to obtain a functional reference to the specified engine, 84thus initialising it if needed. The engine will then be set as the default 85for all available algorithms. 86 87=item B<-primes num> 88 89Specify the number of primes to use while generating the RSA key. The B<num> 90parameter must be a positive integer that is greater than 1 and less than 16. 91If B<num> is greater than 2, then the generated key is called a 'multi-prime' 92RSA key, which is defined in RFC 8017. 93 94=item B<numbits> 95 96The size of the private key to generate in bits. This must be the last option 97specified. The default is 2048 and values less than 512 are not allowed. 98 99=back 100 101=head1 NOTES 102 103RSA private key generation essentially involves the generation of two or more 104prime numbers. When generating a private key various symbols will be output to 105indicate the progress of the generation. A B<.> represents each number which 106has passed an initial sieve test, B<+> means a number has passed a single 107round of the Miller-Rabin primality test, B<*> means the current prime starts 108a regenerating progress due to some failed tests. A newline means that the number 109has passed all the prime tests (the actual number depends on the key size). 110 111Because key generation is a random process the time taken to generate a key 112may vary somewhat. But in general, more primes lead to less generation time 113of a key. 114 115=head1 SEE ALSO 116 117L<gendsa(1)> 118 119=head1 COPYRIGHT 120 121Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 122 123Licensed under the OpenSSL license (the "License"). You may not use 124this file except in compliance with the License. You can obtain a copy 125in the file LICENSE in the source distribution or at 126L<https://www.openssl.org/source/license.html>. 127 128=cut 129