Using Linux commands and OpenSSL for base64 encoding and encryption

You can use the following Linux command-line command and OpenSSL to hash and sign the policy statement, base64-encode the signature, and replace characters that are not valid in URL query string parameters with characters that are valid.

For information about OpenSSL, go to https://www.openssl.org.

cat policy | tr -d "\n" | tr -d " \t\n\r" | openssl sha1 -sign private_key.pem | openssl base64 -A | tr -- '+=/' '-_~'

where:

cat reads the policy file.

tr -d "\n" | tr -d " \t\n\r" removes the white spaces and newline character that were added by cat.

OpenSSL hashes the file using SHA-1 and signs it using RSA and the private key file private_key.pem.

OpenSSL base64-encodes the hashed and signed policy statement.

tr replaces characters that are not valid in URL query string parameters with characters that are valid.

For code examples that demonstrate creating a signature in several programming languages see Code examples for creating a signature for a signed URL.