In my understanding, private keys are encrypted with some symmetric algorithm, so you can't access them without passphrase. What is it called?

  • This isn't specified in the standard. @CBobRobison is correct, Geth in particular uses AES to encrypt its private key, but this can varry from client to client. Most do use AES, because it's so ubiquitous Nov 9, 2016 at 19:49
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    Related: ethereum.stackexchange.com/questions/1825/…
    – eth
    Jan 6, 2017 at 2:14
  • That can be looked up in the JSON file that stores the encrypted private key. It is typically the value of the "cipher" element. For example, in a Parity key file: "cipher": "aes-128-ctr" means 128-bit AES in Counter mode. May 30, 2017 at 23:41

2 Answers 2


The key is encrypted with 128-bit AES in Counter (CTR) mode.

  • How secure is this encryption method considering the improvement to computing power in the next 10 to 20 years? May 20, 2022 at 5:22

Private keys encryption is normally done using Sha algorithm.

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    SHA is not an encryption algorithm, it's a family of hash functions. Nov 9, 2016 at 19:47

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