Compilation of OpenSSL commands required for basic crypto

crypto.sh

## Asymmetric Encryption ##
# generate RSA-2048 private key
openssl genrsa -aes256 -passout pass:passphrase -out private_key.pem 2048
# generate corresponding public key
openssl rsa -in private_key.pem -passin pass:passphrase -pubout -out public_key.pem
# encrypt using public key
openssl rsautl -encrypt -pubin -inkey public_key.pem -in message.txt -out message.txt.encrypted
# decrypt using private key
openssl rsautl -decrypt -inkey private_key.pem -passin pass:passphrase -in message.txt.encrypted -out message.txt.decrypted

## Digital Signature ##
# compute SHA-256 for a file
openssl dgst -sha256 message.txt
# digitally sign the file
openssl dgst -sha256 -sign private_key.pem -passin pass:passphrase -out message.txt.signature message.txt
# convert binary signature to ASCII
openssl base64 -in message.txt.signature -out message.txt.signature_ascii
# convert ASCII signature to binary
openssl base64 -d -in message.txt.signature_ascii -out message.txt.signature
# verify the signature
openssl dgst -sha256 -verify public_key.pem -signature message.txt.signature message.txt

## Symmetric Encryption ##
# encode password to base64 string
openssl base64 <<< "password"
# decode base64 string to password
openssl base64 -d <<< "cGFzc3dvcmQK"
# generate random ASCII string of length 30
openssl rand -base64 30 -out aes_password
# encrypt using AES-256 to get plaintext
openssl enc -aes-256-cbc -in message.txt -out message.txt.encrypted -a -pass file:aes_password
# decrypt plaintext cipher using AES-256
openssl enc -aes-256-cbc -in message.txt.encrypted -out message.txt.decrypted -a -d -pass file:aes_password