The new technology also includes a special application that can be activated if the smart phone is confiscated by security authorities.
The US wants to equip the activists with the new tools to fight back the repressive governments and is targeting countries ranging from the Middle East to China, a newspaper reported.
"We've been trying to keep below the radar on this, because a lot of the people we are working with are operating in very sensitive environments," Michael Posner, assistant US secretary of state for human rights and labour, was quoted as saying.
According to the report, the initiative is part of Secretary of State Hillary Clinton's push to expand Internet freedoms following the pro-democracy movements in Iran, Egypt, Tunisia and elsewhere.
Social networking sites like Facebook and Twitter have played a key role in fuelling all those revolutions.
