環境：
Icon name: computer-vm
Chassis: vm
Machine ID: 6d12c80cd2cb0c409f7a3e4b8c6b71dc
Boot ID: c26be545d2d449f985a3263d896f6d8d
Virtualization: kvm
Operating System: CentOS Linux 7 (Core)
CPE OS Name: cpe:/o:centos:centos:7
Kernel: Linux 3.10.0-1160.49.1.el7.x86_64
Architecture: x86-64
確認
$ yum list | grep openssl
openssl.x86_64 1:1.0.2k-22.el7_9 @updates
openssl-libs.x86_64 1:1.0.2k-22.el7_9 @updates
秘密鍵生成
$ openssl genrsa -des3 -out genrsa-des3.key 2048
Generating RSA private key, 2048 bit long modulus
..............+++
...................................................+++
e is 65537 (0x10001)
Enter pass phrase for sin-rsa-des3.key:
Verifying - Enter pass phrase for sin-rsa-des3.key:
秘密鍵から公開鍵を生成
$ openssl rsa -in genrsa-rsa-des3.key -pubout > pubkey.key
Enter pass phrase for sin-rsa-des3.key:
writing RSA key
RSA形式の公開鍵の内容を確認
$ openssl rsa -puboutin -in sin-rsa-pubkey.key -text
Public-Key: (2048 bit)
Modulus:
00:a6:df:27:3d:5d:c4:e0:85:2e:df:56:ef:f7:85:
<<秘密鍵内容>>
dd:df
Exponent: 65537 (0x10001)
writing RSA key
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEApt8nPV3E4IUu31bv94U8
<<公開鍵内容>>
lrhe8xxh+c/oolAoIHk7AVww1p70e4Z4MTmHz9fnf8y5haUM/b0AueRJosS5tUjd
3wIDAQAB
-----END PUBLIC KEY-----
公開鍵を用いて暗号化
$ openssl rsautl -encrypt -pubin -inkey rsa-pubkey.key -in test -out test-rsa.txt
秘密鍵を用いて復号化
$ openssl rsautl -decrypt -inkey genrsa-des3.key -in test-rsa.txt -out test-decrypt.txt
Enter pass phrase for genrsa-des3.key: