In a community known for its biting, sometimes misogynistic discourse on Twitter, Mr. Kaminsky stood out for his empathy. He disdained Twitter pile-ons and served as a mentor to journalists and aspiring hackers. He would often foot a hotel or travel bill to Black Hat for those who could not afford it. When one protégé broke up with her boyfriend, Mr. Kaminsky bought her a plane ticket to go see the young man, believing they were meant to be. (They married.)

He was outspoken when privacy and security were on the line. After the F.B.I. tried to force Apple, in federal court, to weaken the encryption of its iPhones in 2015, James B. Comey, who was then the F.B.I. director, testified to Congress in 2016 that he was not asking for a backdoor, but for Apple to “take the vicious guard dog away and let us pick the lock.”

“I am that vicious guard dog, and that used to be a compliment,” Mr. Kaminsky told this reporter at the time. “The question for Mr. Comey is: What is the policy of the United States right now? Is it to make things more secure or to make them less secure?”

The Electronic Frontier Foundation, a group that promotes civil liberties, said in a tweet on Saturday that Mr. Kaminsky had been a “friend of freedom and embodiment of the true hacker spirit.” Jeff Moss, the founder of the DefCon and Black Hat hacking conferences, suggested that Mr. Kaminsky be inducted into the Internet Hall of Fame.

Mr. Kaminsky’s generosity extended to his many side projects. When a friend struggled with color blindness, he developed the DanKam, a mobile app that uses a phone’s camera to decipher colors otherwise indecipherable to the colorblind. When his grandmother Raia Maurer, now 97, experienced hearing loss, he refocused his efforts on hearing-aid technology.

And when his aunt, a dermatologist, told him that she could no longer treat under-resourced patients for AIDS-related skin diseases, some potentially fatal, in sub-Saharan Africa and Rohingya refugee camps, Mr. Kaminsky helped develop telemedicine tools for the National Institutes of Health and AMPATH, a health project led by Indiana University that he sought to bring to San Francisco during the coronavirus pandemic.

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