Early private key

External question — Bitcoin Stack Exchange Author: roy Original post: https://bitcoin.stackexchange.com/questions/130952 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. In the beginning, when you didn't use bitcoin-qt, so no wallet.dat or anything, and WIF wasn't a thing back then, you could write down your 64 hex characters as your private key, but was hmac-sha256 also valid? so you had a secret key(utf-8/latin1) and a utf-8/latin-1 input of 32 characters /bytes

External answer — Bitcoin Stack Exchange Author: RedGrittyBrick Original post: https://bitcoin.stackexchange.com/a/130954 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. tl;dr: No. you could write down your 64 hex characters as your private key, This seems to me to be a back-to-front way of looking at this. A private key is simply a large number. That is all. Encodings There are lots of ways of writing down a number. For example "fifteen" and "15" are two completely different ways of writing down the same number. They are two different ways of writing a number that can be used as a private key. "fifteen" and "15" look different but they are the same private key, not two different private keys. The example "15" is a way of writing a number as a sequence of digits from a finite set. The set has ten members 0 1 2 3 4 5 6 7 8 9. Because this set has ten members we call it decimal , from Latin decimalis meaning tenths. We can also write the same number as a sequence of digits from a different set. If we choose the set 0 1 2 3 4 5 6 7 8 9 A B C D E F, we can write the number fifteen as "F" . To make this less ambiguous we might indicate that this set is used by writing "F" as, for example, "xF", "0xF", "0x0F" or F 16 . This set of digits has sixteen members so we call it hexadecimal from Greek hexa meaning six and Latin decimalis meaning ten. If I remember correctly, WIF uses a set of 58 digits (by using symbols we usually regard as alphabetic as digits). We call that set base58 , you can write fifteen or any other number in base58. It is useful for large numbers because the written form is shorter when you have larger sets of digits to use. Character sets UTF8 and Latin1 are two different character-encodings of two different character-sets. They have no effect on any of the above ways of encoding numbers. They are irrelevant here. Encoding vs Encryption The word encoding has different meanings in different contexts but here it refers only to a way of writing down a number. Encryption is a way of deliberately hiding some message or other data by converting it into something that is unreadable but which can be transformed back into the original form, usually with the use of an encryption-key and an encryption algorithm. Encoding is not encryption. Hashing By contrast with various encodings, SHA256 is not a way of writing down a number. It is not an encoding of a number. SHA256 is a hash function. It is a way of producing a second number from a number. This is not a way to write down a key because you cannot mathematically calculate the first number from the second. You cannot calculate the key from the hash. You lost the key. Therefore ... was hmac-sha256 also valid? No. Not as a way of storing a private key.