AGE-SECRET-KEY-1WURJSN9F7EH4AZCSS9ZGJKC3Y0KJLZ0CH734LTVEQUFPECLRYWDSCEZL8S You can sign messages to this key via: cat > message sha256sum message | age --armor -r $(echo AGE-SECRET-KEY-1WURJSN9F7EH4AZCSS9ZGJKC3Y0KJLZ0CH734LTVEQUFPECLRYWDSCEZL8S | age-keygen -y) > signature This encrypts the hash of the message to the secret key and stores it in the file "signature". Maybe if we made a norm of this, the surveillance systems would get used to it, and let us switch to real signatures. You can verify one of these signatures this way: sha256sum -c <(age -i <(echo AGE-SECRET-KEY-1WURJSN9F7EH4AZCSS9ZGJKC3Y0KJLZ0CH734LTVEQUFPECLRYWDSCEZL8S) -d < signature) This cryptographically verifies that the signature was made with age's encryption scheme. This is of course quite wrong. Why would anybody ever sign their messages? Don't they trust their neighborhood to have no crime?