Users of encryption technology can no longer refuse to reveal keys to UK authorities after amendments to the powers of the state to intercept communications took effect this week, reports legal website out-law.com.
The Regulation of Investigatory Powers Act (RIPA) has had a clause activated which allows a person to be compelled to reveal a decryption key. Refusal can earn someone a five-year jail term.
Part III of RIPA was in the original act but was not activated. The Home Office said last year that it had not implemented the provision because encryption had not been as popular as quickly as it had predicted.
It launched a consultation which culminated in Part III being made active on 1 October.
The measure has been criticised by civil liberties activists and security experts who say that the move erodes privacy and could lead a person to be forced to incriminate themselves.
It is also controversial because a decryption key is often a long password - something that might be forgotten. An accused person might pretend to have forgotten the password, or he might genuinely have forgotten it, but struggle to convince a court to believe him.
Section 49 of Part III of RIPA compels a person, when served with a notice, to either hand over an encryption key or render the requested material intelligible by authorities.
Anyone who refuses to decrypt material could face five years in jail if the investigation relates to terrorism or national security, or up to two years in jail in other cases.
The Home Office said the process will be overseen by the Interception of Communications Commissioner, the Intelligence Services Commissioner and the Chief Surveillance Commissioner.