feat: sign, verify

README.md

@@ -27,7 +27,7 @@ hW53WfImja+b5kwwyqUikyMCAwEAAQ==
 
 encrypt
 ```
-openssl rsautl -encrypt -pubin -inkey enc_key.pem -in test.txt -out enc.txt -pkcs
+$ openssl rsautl -encrypt -pubin -inkey enc_key.pem -in test.txt -out enc.txt -pkcs
 ```
 
 decrypt
@@ -35,6 +35,19 @@ decrypt
 $ cargo r -- pgp-card-decrypt -c $(cat enc.txt | xxd -ps -c 11111)
 ```
 
+## sign
+
+sign
+```
+$ cargo r -- pgp-card-sign -2 $(shasum -a 256 test.txt  | awk '{print $1}')
+```
+
+verify
+```
+$ openssl dgst -sha256 -verify sign_key.pem -signature sig test.txt 
+Verified OK
+```
+
 
 Awesome webauthn:
 * https://github.com/herrjemand/awesome-webauthn