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openssl — OpenSSL cryptographic toolkit. Some subcommands such as `req` have their own usage documentation. Mo

Submitted by: @import:tldr-pages·Mar 2, 2026·

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Problem

How to use the openssl command: OpenSSL cryptographic toolkit. Some subcommands such as req have their own usage documentation. More information: <https://docs.openssl.org/master/man1/openssl/>.

Solution

openssl — OpenSSL cryptographic toolkit. Some subcommands such as req have their own usage documentation. More information: <https://docs.openssl.org/master/man1/openssl/>.

Generate a private key and encrypt the output file using AES-256:

openssl genpkey -algorithm {{rsa|ec}} -out {{path/to/private.key}} -aes256

Generate the corresponding public key from the private key private.key using rsa:

openssl rsa -in {{path/to/private.key}} -pubout -out {{path/to/public.key}}

Generate a self-signed certificate valid for a specified number of days (365):

openssl req -new -x509 -key {{path/to/private.key}} -out {{path/to/certificate.crt}} -days 365

Convert a certificate to .pem or .der format:

openssl x509 -in {{path/to/certificate.crt}} -out {{path/to/certificate.pem|path/to/certificate.der}} -outform {{pem|der}}

Check certificate details:

openssl x509 -in {{path/to/certificate.crt}} -text -noout

Generate a certificate signing request (CSR):

openssl req -new -key {{path/to/private.key}} -out {{path/to/request.csr}}

Display help:

openssl help

Display version:

openssl version

Code Snippets

Generate a private key and encrypt the output file using AES-256

openssl genpkey -algorithm {{rsa|ec}} -out {{path/to/private.key}} -aes256

Generate the corresponding public key from the private key `private.key` using `rsa`

openssl rsa -in {{path/to/private.key}} -pubout -out {{path/to/public.key}}

Generate a self-signed certificate valid for a specified number of days (365)

openssl req -new -x509 -key {{path/to/private.key}} -out {{path/to/certificate.crt}} -days 365

Convert a certificate to `.pem` or `.der` format

openssl x509 -in {{path/to/certificate.crt}} -out {{path/to/certificate.pem|path/to/certificate.der}} -outform {{pem|der}}

Check certificate details

openssl x509 -in {{path/to/certificate.crt}} -text -noout

Context

tldr-pages: common/openssl

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