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I am trying to understand what is the private key in Ethereum. Help please.

  1. Private key = the address?
  2. Private key = the password/passphrase?
  3. Private key = the text seen when we open the file in the keystore folder?
  4. Private key = something other than the above?
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  • Besides the answers below, here is an answer that will help you understand how the private key is stored in the file in the keystore folder. ethereum.stackexchange.com/questions/15494/…
    – Ajoy Bhatia
    Jul 4, 2017 at 18:43
  • Note: I've edited the title from "Where...?" to "What...?". The question itself is asking what the private key is, not where it's kept.
    – Richard Horrocks
    Jul 4, 2017 at 21:28
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    @RichardHorrocks: See scam attempt in the answer that was posted here yesterday.
    – goodvibration
    Dec 17, 2020 at 8:40

3 Answers 3

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in short :

the private key(secret big number) is created by your wallet randomly, then encrypted(with you password) and stored in the UTC file in the keystore folder. the address is calculated from the public key which is derived from the private key.

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    When you say " ... public key which is deactivated from the private key ... ", I think that you mean "derived from the private key".
    – Ajoy Bhatia
    Jul 4, 2017 at 18:39
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    exactly sorry for the awfull typo
    – Badr Bellaj ♦
    Jul 4, 2017 at 18:44
  • And when I am asked to type in my private key — what exactly do I need to type in?
    – Martin
    May 17, 2018 at 10:46
  • Why does that matter? I just want my private key decrypted in clear text. Is that to much to ask? But to put your mind at rest: Minds.com which currently runs on the Rinkeby test net. So no real money is at risk.
    – Martin
    May 17, 2018 at 10:52
  • your private key is a number between 0 to 2^256 (32 bytes), it's usually represented in 64 hex characters or 32 ASCII characters, but as ASCII it wouldn't be clear text, it'll look like mambo jambo.
    – Kof
    Jun 6, 2022 at 18:33
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To get a better understanding of what a private key in Ethereum is, you need to understand what Asymmetric cryptography is. https://en.wikipedia.org/wiki/Public-key_cryptography

There are two popular asymmetric cryptography algorithms. RSA and ECDSA. Ethereum uses ECDSA (Elliptic Curve Digital Signature Algorithm). You can see how ECDSA functions here. https://blog.cloudflare.com/a-relatively-easy-to-understand-primer-on-elliptic-curve-cryptography/

To put the above in perspective in simple terms - A private key is a very large random number that is used to generate a public key. This public key is used to create your address on the Ethereum blockchain. The private key allows you to sign transactions. These transactions can be verified by other participants on the chain against your Public key.

To better educate yourselves, use the link below to generate your private key on your own machine and derive your address on the Ethereum network. https://kobl.one/blog/create-full-ethereum-keypair-and-address/

Now a private key is very hard to remember, so wallets allow you to store your private key in them secured with a password (using symmetric cryptography). What this means is, you can sign your transaction on that same wallet instance using an easy to remember the password. It is very important to understand that this password is not your private key, and if you lose access to this wallet, your password will not allow you to retrieve the private key from other wallets.

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    And how do I decrypt the private key from my wallet? Why is everybody dancing around answering that question.
    – Martin
    May 17, 2018 at 10:55
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    You can decrypt your encrypted private key with your wallet password.
    – Omkar Khair
    May 18, 2018 at 4:08
  • is it legal to know the private key? is there any alternative?
    – Md. Nahiduzzaman Rose
    Jun 24, 2021 at 5:44
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If you compare the private key and public key concept with web2 space, then think of like your Gmail account, your Gmail address is your public key, which you can share with anyone so that anyone can mail you easily, and your password is your private key, which you can't share, if it's stolen then your wallet or can say your Gmail account get hacked.

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