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Kishan B
Kishan B

Posted on • Originally published at kishaningithub.github.io

Openssl by Example

#security #tooling #linux #openssl

Table of contents

Symmetric key

Encryption 

$ echo "top secret text" | openssl enc -aes-256-cbc -base64
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
<< encrypted text >>
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Decryption 

$ echo "<< encrypted text >>" | openssl enc -d -aes-256-cbc -base64
enter aes-256-cbc decryption password:
top secret text
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Asymmetric key

Key Generation

Public key 

openssl genrsa -out private.pem 2048
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Private key 

openssl rsa -in private.pem -pubout -out public.pem
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Encryption 

openssl rsautl -encrypt -in secret-transmission.txt -out secret-transmission.txt.enc -inkey public.pem -pubin
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Decryption 

openssl rsautl -decrypt -in secret-transmission.txt.enc -out secret-transmission.txt -inkey private.pem
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Sending signed messages 

openssl rsautl -sign -in secret-transmission.txt -out secret-transmission.txt.enc.signed -inkey private.pem
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Reading signed messages 

openssl rsautl -verify -in secret-transmission.txt.enc.signed -out secret-transmission.txt -inkey public.pem -pubin
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Encrypting private key

Never store private key in clear text format!

openssl rsa -in private.pem -des3 -out private-enc.pem
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Others

Find openssl version 

$ openssl version
LibreSSL 2.6.4
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List ciphers 

openssl list-cipher-commands
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