The government’s statement claims possession of the documents by Mr Miranda, Mr Greenwald and the Guardian posed a threat to national security, particularly because Mr Miranda was carrying a password alongside a range of electronic devices on which classified documents were stored.
Keeping passwords separate from the computer files or accounts to which they relate is a basic security step.
Oliver Robbins, the deputy national security adviser for intelligence, security and resilience in the Cabinet Office, said in his 13-page submission: “The information that has been accessed consists entirely of misappropriated material in the form of approximately 58,000 highly classified UK intelligence documents.
“I can confirm that the disclosure of this information would cause harm to UK national security.
“Much of the material is encrypted. However, among the unencrypted documents … was a piece of paper that included the password for decrypting one of the encypted files on the external hard drive recovered from the claimant.
“The fact that … the claimant was carrying on his person a handwritten piece of paper containing the password for one of the encrypted files … is a sign of very poor information security practice.”
He added: “Even if the claimant were to undertake not to publish or disclose the information that has been detained, the claimant and his associates have demonstrated very poor judgement in their security arrangements with respect to the material rendering the appropriation of the material, or at least access to it by other, non-State actors, a real possibility.”
The government has been forced to assume that copies of the information held by Mr Snowden, who worked for the US National Security Agency, are now in the hands of foreign governments after his travel to Moscow via Hong Kong, Mr Robbins said.
Disclosure of the material could put the lives of British intelligence agents or their families at risk, the court heard, and the general public could also be endangered if details about intelligence operations or methods fell into the wrong hands.
Another statement by a senior officer from Scotland Yard’s Counter Terrorism Command, SO15, disclosed police have so far only reconstructed 75 of the 58,000 classified documents which Mr Miranda was carrying.
In her statement to the court Detective Superintendent Caroline Goode said the encrypted files were “extremely difficult to access”.
Mr Miranda’s computer hard drive contained 60 gigabytes of data of which only 20 have been accessed so far, she said, and police have established the documents contained material that was classified to the “highest levels”.
It was also confirmed for the first time that GCHQ, the government’s listening post, is helping Scotland Yard decrypt the files seized from Mr Miranda.
Both sides agreed to a temporary court order continuing until a full hearing takes place in October.
Alan Rusbridger, editor-in-chief of Guardian News & Media, said: “Mr Robbins makes a number of unsubstantiated and inaccurate claims in his witness statement.
“The way the government has behaved over the past three months belies the picture of urgency and crisis they have painted.”
He said officials in this country and the US had delayed contacting other organisations about GCHQ material, including the New York Times.
“This five week period in which nothing has happened tells a different story from the alarmist claims made by the government in their witness statement,” said Mr Rusbridger.
“The Guardian took every decision on what to publish very slowly and very carefully and when we met with government officials in July they acknowledged that we had displayed a ‘responsible’ attitude.
“The government’s behaviour does not match their rhetoric in trying to justify and exploit this dismaying blurring of terrorism and journalism.”
Gwendolen Morgan, Mr Miranda’s solicitor, said: “Given the vague doomsday prophesies which the police and Home Office have put before the court, our client decided that the full hearing in October was the better forum in which to argue these fundamental issues of press freedom.
“He hopes that – in open court – the defendants’ assertions will be fully tested.”
Mr Miranda said in a statement: “I am bringing this case because I believe that my rights have clearly been violated by UK authorities, and that basic press freedoms are now threatened by the attempted criminalization of legitimate journalistic work.”
Mr Greenwald said: “The UK Government is incapable of pointing to a single story we have published that has even arguably harmed national security.
“The only thing that has been harmed are the political interests and reputations of UK and US officials around the world, as they have been caught engaging in illegal, unconstitutional and truly dangerous bulk surveillance aimed at their own citizens and people around the world, all with little accountability or transparency – until now.
“The government’s accusation that we have been irresponsible with the security measures we took with the materials with which we are working are negated by their own admission that they have been unable to obtain access to virtually any of the documents they seized from Mr Miranda because, in the government’s words, those materials are ‘heavily encrypted’.”
A Scotland Yard spokeswoman said: “As previously stated the Metropolitan Police Service Counter Terrorism Command is now carrying out a criminal investigation, which is at an early stage.”
