% java keytool, certificate, encryption

## Creating
# Generate a Java keystore and key pair
keytool -genkey -alias <ALIAS> -keyalg RSA -keystore <OUTPUT_JKS> -keysize <RSA_LENGTH>

# Generate a certificate signing request (CSR) for an existing Java keystore
keytool -certreq -alias <ALIAS> -keystore <INPUT_JKS> -file <OUTPUT_CSR>

# Import a root or intermediate CA certificate to an existing Java keystore
keytool -import -trustcacerts -alias root -file <INPUT_CRT> -keystore <INPUT_JKS>

# Import a signed primary certificate to an existing Java keystore
keytool -import -trustcacerts -alias <ALIAS> -file <INPUT_CRT> -keystore <INPUT_JKS>

# Generate a keystore and self-signed certificate
keytool -genkey -keyalg RSA -alias <ALIAS> -keystore <OUTPUT_JKS> -storepass <PASSWORD> -validity <VALIDITY> -keysize <RSA_LENGTH>



## Verifying
# Check a stand-alone certificate
keytool -printcert -v -file <INPUT_CRT>

# Check which certificates are in a Java keystore
keytool -list -v -keystore <INPUT_JKS>

# Check a particular keystore entry using an alias
keytool -list -v -keystore <INPUT_JKS> -alias <ALIAS>



## Other
# Remove a certificate from a keystore
keytool -delete -alias <ALIAS> -keystore <INPUT_JKS>

# Change the password of a keystore
keytool -storepasswd -keystore <INPUT_JKS> -new <NEW_PASSWORD>

# Export a certificate from a keystore
keytool -export -alias <ALIAS> -file <OUTPUT_CRT> -keystore <INPUT_JKS>

# List the trusted CA Certs from the default Java Trusted Certs Keystore
keytool -list -v -keystore $JAVA_HOME/jre/lib/security/cacerts

# Import New Certificate Authority into the default Java Trusted Certs Keystore
keytool -import -trustcacerts -file <INPUT_PEM> -alias <ALIAS> -keystore $JAVA_HOME/jre/lib/security/cacerts



# Sensible/common default alternatives
$ VALIDITY: printf "DAYS\tCOMMENT\n1\ta day\n30\ta month\n365\ta year\n730\ttwo years" --- --column 1 --headers 1
$ RSA_LENGTH: printf "KEY LENGTH\tCOMMENT\n2048\t\tDefault\n4096\t\tBetter\n8192\t\tSlow?" --- --column 1 --headers 1

# Attempt to find files with the appropriate endings, default to everything.
$ INPUT_CRT:    ls -a | grep -e "\(.crt\|.cer\|.der\)" || ls -a
$ INPUT_PEM:    ls -a | grep -e "\(.pem\)"             || ls -a
$ INPUT_JKS:    ls -a | grep -e "\(.jks\)"             || ls -a