In the on­go­ing de­bate between law en­force­ment and the tech­no­logy com­munity over en­cryp­tion, the threat of ter­ror­ism in the home­land has long been the ace in the FBI’s hand.

FBI Dir­ect­or James Comey has in re­cent months re­peatedly asked tech com­pan­ies to cre­ate products that al­low law en­force­ment to ac­cess en­cryp­ted com­mu­nic­a­tions if they first ob­tain a war­rant, warn­ing that strong en­cryp­tion al­lows ter­ror sus­pects to plot “in the dark.”

Speak­ing be­fore the Sen­ate Home­land Se­cur­ity Com­mit­tee Thursday, Comey said the threat of homegrown ter­ror­ism has brought the tech in­dustry to the table to talk about ways to co­oper­ate with law en­force­ment over en­cryp­tion.

“I think, in part, the ISIL threat fo­cused every­body’s minds,” Comey said, and con­vinced op­pon­ents that “we’re really not just mak­ing this up.”

The De­part­ment of Justice has in the past de­murred when asked to ap­prox­im­ate the scale of what of­fi­cials of­ten call the “go­ing dark prob­lem.” But pressed by com­mit­tee chair­man Ron John­son on how many ter­ror sus­pects his agents have ac­tu­ally lost track of be­cause of en­cryp­tion, Comey on Wed­nes­day gave the closest thing to a stat­ist­ic that the de­part­ment has pub­licly shared.

“Prob­ably the best num­ber I can give in an open set­ting is dozens,” Comey said.

John­son seemed taken aback at the re­sponse and moved on to ask an­oth­er ques­tion. Later, he re­turned to the FBI dir­ect­or’s an­swer.

“I’m a little con­cerned about num­bers, but I will say, I’m sur­prised if it is only a couple dozen people who have been in­spired by so­cial me­dia and then moved in­to en­cryp­ted ac­counts,” John­son said.

Pre­vi­ously, the Justice De­part­ment’s Kir­an Raj has ex­pressed a need for bet­ter pub­lic data about the num­ber of cases af­fected by strong en­cryp­tion.

“We need to do a bet­ter job ex­plain­ing how many cases are af­fected by this,” Raj, the seni­or coun­sel to the deputy at­tor­ney gen­er­al, said at a pan­el dis­cus­sion last month hos­ted by Geor­getown Uni­versity and Just Se­cur­ity.

Pres­sure has in­creased in re­cent weeks against the FBI’s push for ac­cess to en­cryp­ted mes­sages.

This month, two former NSA dir­ect­ors—Mi­chael Mc­Con­nell and Mi­chael Hay­den—said they sup­port strong en­cryp­tion, and pushed law en­force­ment to find an­oth­er way to do its job. And the tech com­munity has ramped up calls for the White House to come out against “back doors” that would al­low the FBI to read en­cryp­ted com­mu­nic­a­tions.

Mean­while, Comey is car­ry­ing on his charm of­fens­ive. Even as he asked if the tech com­munity has “really tried” to solve the prob­lem at a hear­ing last month, he main­tained that law en­force­ment and tech com­pan­ies share com­mon goals.

To prove the point, Comey likes to re­peat that his agency is not “an ali­en force im­posed on the Amer­ic­an people.”

“The con­ver­sa­tions are on­go­ing and they’ve got­ten health­i­er,” he said Wed­nes­day. “People have stripped out a lot of the venom. Folks aren’t ques­tion­ing as much as they used to each oth­er’s motives. Cause we’re in a place where we re­cog­nize we care about the same stuff.”