Here is a list of US patents for key escrow systems: 380/286 [1]. It is important to know that key escrow does not itself mean that the keys are escrowed to law

Here is a list of US patents for key escrow systems: 380/286 [1]. It is important to know that key escrow does not itself mean that the keys are escrowed to law enforcement, but in many cases it is obvious or it is spelled out explicitly: "In order to receive the information, law enforcement may submit a request to each of the entities identifying the communication session and their basis for authorization." [2] It is also important to know that law enforcement escrow systems may also apply under different categories, so this list has both type 1 and type 2 error. The number of companies on the list is huge and include essentially all of the 'blockbuster' names in the tech industry, from IBM to Amazon to Fujitsu to Seagate to Apple to Symantec to F-Secure, etc. (I have a longer list here, although it has not been combed for law enforcement escrow and it is also not representative of the names on the patent search list [3]). Care must be taken to discern which patents would have applicability to serve orders such as those by National Security Letters or to comply with the decryption requirements of CALEA. There's some scary stuff in there, like "Automatic recovery of TPM keys" (Lenovo) [4] and "Cloud key escrow system" (Microsoft) [5]. HP obtained a patent (in 2008) for PC backdoors [6]. [1] https://www.google.com/search?tbm=pts&hl=en&q=uspclass%3A%22380%2F286%22 https://www.google.com/search?tbm=pts&hl=en&q=uspclass%3A%22... [2] https://www.google.com/patents/EP2637350A2 https://www.google.com/patents/EP2637350A2 [3] https://news.ycombinator.com/item?id=8452070 https://news.ycombinator.com/item?id=8452070 [4] https://www.google.com/patents/US8290164 https://www.google.com/patents/US8290164 [5] https://www.google.com/patents/US20120321086 https://www.google.com/patents/US20120321086 [6] https://www.google.com/patents/EP1059578A2 https://www.google.com/patents/EP1059578A2