Instead, RelayRides is trusting that the owner and renter would arrange ways to hand over keys before and after rentals.
ISPs were anxious about the cost of developing interception equipment, and some firms were worried that handing over keys would threaten their own security.
The sign-up process for RelayRides has been streamlined for OnStar users, and OnStar-equipped cars can be locked and unlocked by renters using an app, so there is no need to meet to hand over keys.
The company hopes to e able to begin handing over keys to its first pre-order customers in 2019, once all its certifications are complete.
Speaking to the BBC, Silent Circle co-founder Phil Zimmermann said the service was closed because of Lavabit's action and because it feared it would be coerced into handing over keys that can unscramble messages.
When the court reaches its verdict, which could take weeks, it could set a precedent for whether US law enforcement agencies can in future compel firms to hand over keys to unlock all of their data.
An advocacy group is suing to force the federal government to hand over key records from an investigation into allegations of sexual abuse at a family detention center in Texas.
It was because the Guardian had subpoenaed Mr Major and Michael Heseltine to give evidence in the case that the government handed over key documents to the newspaper's lawyers, Geoffrey Robertson, QC, and Geraldine Proudler.
Senator Patrick Leahy, chairman of the Judiciary Committee, said yesterday that the Senate would be reluctant to confirm Mr. Mukasey until the White House handed over key documents on issues like domestic surveillance.
The prosecution complains that Kenya is refusing to hand over key documents, which they say contain evidence of Kenyatta's involvement in post-election violence in 2007 and 2008, when he was supporting the then president Mwai Kibaki.
