Private key is a number. Is the question positive or negative? Is it possible to know a positive private key or negative if you only know the public key?

For instance:

Positive private key: 2

public key:



public key:


Now I will write two public keys to "3" and "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD036413E":



How to determine which is a positive and which is a negative private key to these two public keys?

1 Answer 1


There really isn't a "positive" or "negative" for private keys. Private keys are unsigned integers, so they're basically all "positive". Your "negative" numbers are not actually negative, they're the modular additive inverse of the "positive" private key.

Since private keys are really unsigned integers, you can't glean any information about signed-ness from the public key because there are no signs to even look at. Every private key is the "negative" of another private key, so a private key is both "positive" and "negative". Every private key has an additive inverse.

However, given two public keys, you can determine whether their private keys are additive inverses of each other by checking whether the X coordinates are the same. If so, one should have a Y coordinate that is odd, and the other have a Y coordinate that is even. This only tells you that their private keys are additive inverses of each other. But you won't know which is the lower number or what one of them is (unless you have the private key for one of them).

  • Can I get the positive private key from the negative key? Commented Sep 13, 2021 at 22:00
  • Please help. I need to do this kotlin or java Commented Sep 14, 2021 at 9:57
  • you can invert the private key within the field, yes Commented May 22, 2023 at 3:13

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