diff -r 85b6f13f1088 -r 12acb6c02d32 src/lib/GenericASN1ContentHandler.h
--- a/src/lib/GenericASN1ContentHandler.h	Thu Jul 22 20:01:03 2021 +0200
+++ b/src/lib/GenericASN1ContentHandler.h	Wed Jul 28 01:40:05 2021 +0200
@@ -39,6 +39,8 @@
 	XMLContentHandlerProxy handlers;
 
 	std::string rootName = "asn1";
+	std::string bitStringSymbol0 = "0";
+	std::string bitStringSymbol1 = "1";
 	bool treeWithNamespaces = false;
 
 	/**
@@ -98,6 +100,8 @@
 		else if (uri == xml::TreeWithNamespaces) treeWithNamespaces = parseBoolean(value);
 		else if (uri == xml::TreeStyle && value == "standard"); // the only style currently supported
 		else if (uri == xml::TreeStyle && value == "literal") throw std::invalid_argument("Tree style 'literal' is not yet supported"); // will require ASN.1 schema, might be implemented in another class
+		else if (uri == xml::BitStringSymbol0) bitStringSymbol0 = value;
+		else if (uri == xml::BitStringSymbol1) bitStringSymbol1 = value;
 		else if (uri == xml::TreeStyle) throw std::invalid_argument("Unsupported tree-style: " + value);
 		else return false;
 
@@ -165,8 +169,7 @@
 
 	void writeBitString(const Header& header, std::vector<bool> value) override {
 		std::stringstream bits;
-		for (bool b : value) bits << (int) b;
-		// for (bool b : value) bits << (b ? ':' : '.'); // TODO: configurable true/false symbols?
+		for (bool b : value) bits << (b ? bitStringSymbol1 : bitStringSymbol0);
 		handlers.writeStartElement("bit-string", getCommonAttributes(header,{"length", std::to_string(value.size())}));
 		handlers.writeCharacters(bits.str());
 		handlers.writeEndElement();