US wiretaps were beaten by encryption almost a quarter of the time it was encountered last year, in a small but growing trend of American police snooping.
Cryptography has mostly affected police wiretapping during the last two years, with police encountering encryption 15 times in 2012 and 41 times the subsequent year, and beaten by it four and nine times respectively.
Encryption was involved in only a tiny proportion of more than 3,500 wiretaps authorised last year, in a finding that has led some to claim early fears from police the availability of encryption tools for use by criminals were unfounded.
Matt Blaze, associate professor of computer science at the University of Pennsylvania, said: "So the cryptapocalypse they warned us about in the 90s has come to pass. Strong crypto [was] used in a whopping 0.25% of wiretaps last year.
"It isn't ever clear to me what the wiretap report means when they talk about 'encountering' encryption."
Included in the report was a note on 52 cases involving encryption from past years, unreported until 2013, with police able to decipher the communications in all 52 instances.
"Some of the prosecutors' reports were received too late to include in this document, and some prosecutors may have delayed filing reports to avoid jeopardizing ongoing investigations," the report added. "Information about these wiretaps should appear in future reports."
Drug related crime was specified in more than 3,000 applications for wiretapping, with other offences specified including murder, assault and racketeering far less common reasons for snooping.