1 =pod 2 3 =head1 NAME 4 5 openssl-genrsa, 6 genrsa - generate an RSA private key 7 8 =head1 SYNOPSIS 9 10 B<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 36 The B<genrsa> command generates an RSA private key. 37 38 =head1 OPTIONS 39 40 =over 4 41 42 =item B<-help> 43 44 Print out a usage message. 45 46 =item B<-out filename> 47 48 Output the key to the specified file. If this argument is not specified then 49 standard output is used. 50 51 =item B<-passout arg> 52 53 The output file password source. For more information about the format 54 of 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 58 These options encrypt the private key with specified 59 cipher before outputting it. If none of these options is 60 specified no encryption is used. If encryption is used a pass phrase is prompted 61 for if it is not supplied via the B<-passout> argument. 62 63 =item B<-F4|-3> 64 65 The public exponent to use, either 65537 or 3. The default is 65537. 66 67 =item B<-rand file...> 68 69 A file or files containing random data used to seed the random number 70 generator. 71 Multiple files can be specified separated by an OS-dependent character. 72 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 73 all others. 74 75 =item [B<-writerand file>] 76 77 Writes random data to the specified I<file> upon exit. 78 This can be used with a subsequent B<-rand> flag. 79 80 =item B<-engine id> 81 82 Specifying an engine (by its unique B<id> string) will cause B<genrsa> 83 to attempt to obtain a functional reference to the specified engine, 84 thus initialising it if needed. The engine will then be set as the default 85 for all available algorithms. 86 87 =item B<-primes num> 88 89 Specify the number of primes to use while generating the RSA key. The B<num> 90 parameter must be a positive integer that is greater than 1 and less than 16. 91 If B<num> is greater than 2, then the generated key is called a 'multi-prime' 92 RSA key, which is defined in RFC 8017. 93 94 =item B<numbits> 95 96 The size of the private key to generate in bits. This must be the last option 97 specified. The default is 2048 and values less than 512 are not allowed. 98 99 =back 100 101 =head1 NOTES 102 103 RSA private key generation essentially involves the generation of two or more 104 prime numbers. When generating a private key various symbols will be output to 105 indicate the progress of the generation. A B<.> represents each number which 106 has passed an initial sieve test, B<+> means a number has passed a single 107 round of the Miller-Rabin primality test, B<*> means the current prime starts 108 a regenerating progress due to some failed tests. A newline means that the number 109 has passed all the prime tests (the actual number depends on the key size). 110 111 Because key generation is a random process the time taken to generate a key 112 may vary somewhat. But in general, more primes lead to less generation time 113 of a key. 114 115 =head1 SEE ALSO 116 117 L<gendsa(1)> 118 119 =head1 COPYRIGHT 120 121 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 122 123 Licensed under the OpenSSL license (the "License"). You may not use 124 this file except in compliance with the License. You can obtain a copy 125 in the file LICENSE in the source distribution or at 126 L<https://www.openssl.org/source/license.html>. 127 128 =cut 129
Indexes created Sun Aug 02 00:25:04 UTC 2026