A United Nations report says encryption software that makes it hard to spy on what people do and say online is "essential" for free speech.
It says that without making making tools online anonymous, many people will find it harder to express opinions without being censored.
The report comes as many governments seek to put "backdoors" in encryption software to aid law enforcement.
A report written by David Kaye, a special rapporteur in the UN's office of the high commissioner for human rights, said: "Encryption and anonymity, separately or together, create a zone of privacy to protect opinion and belief."
It also says the tools to create such protection are essential given the "unprecedented capacity" governments, companies, thieves and pranksters now have to interfere with people's ability to express themselves.
It also adds that lacking such tools will mean many people will not be able to "fully explore the basic aspects of their identity" such as gender, ethnicity, race, religion or sexuality.
The report acknowledged the need for police forces and other agencies to access encrypted messages and other forms of communications - but says it should be done on a "case by case" basis and should not be applied to a "mass of people".
The report also warns against the use of backdoors and weak encryption systems that can put anonymity in danger as much as they aid law enforcement.
The report from Mr Kaye is due to be presented to the UN's Human Rights Council in June.
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