pemEncode function
Wraps der in a PEM -----BEGIN [label]----- block, the base64 body
hard-wrapped at 64 columns (RFC 7468). The inverse of pemBytes.
Implementation
String pemEncode(String label, List<int> der) {
final body = base64.encode(der);
final lines = [
for (var i = 0; i < body.length; i += 64)
body.substring(i, i + 64 > body.length ? body.length : i + 64),
];
return '-----BEGIN $label-----\n${lines.join('\n')}\n-----END $label-----\n';
}