in PEM format signature = Popen(["openssl", "sha1", "-sign", key, input], stdout=PIPE).stdout.read(...); # Convert the PEM key to DER (and extract the public form) for inclusion in the CRX header derkey...= Popen(["openssl", "rsa", "-pubout", "-inform", "PEM", "-outform", "DER", "-in", key], stdout=PIPE)...the PEM key to DER....byte[] zipData = File.ReadAllBytes(zipFile); // Read the DER key.