Private Key format

[Alicatraz]

Greetings,
I am a little puzzled , I found this private key and address but I am unable to recognize the format :

private key 5vUtxFj43b4BM6t5dyXnLFEKLbXv8nB75fDFNRZLj7t7Vurvh address 3Nx***********************
anyone knows what it is  ? the address contains 2.9 coins

[Alicatraz]

it looks like an RSA private key but I am not sure why it is next to a bitcoin address ?

[pooya87]

That does look like a bitcoin private key except that it is missing 2 characters since the correct length of an uncompressed private key is 51 not 49.
How did you "find" this anyway? Because if it really did contain 2.9 BTC you wouldn't just come across it. This looks like a fake thing since I checked and no combination of these characters with 2 at different positions could be a valid private key either.

[nc50lc]

private key 5vUtxFj43b4BM6t5dyXnLFEKLbXv8nB75fDFNRZLj7t7Vurvh address 3Nx***********************
anyone knows what it is  ? the address contains 2.9 coins

Don't know, but it couldn't be a WIF private key of that address.
Because the address appears to be a "P2SH-SegWit" and the the private key looks like in WIF uncompressed format.
If anything like it, the coins can't be spent in a standard way.

If it's something like other P2SH like MultiSig, then it may be a prvKey with missing characters of a single cosigner or just a clue to the private keys,
I can't tell, try this thread: [overview] Recover Bitcoin from any old storage format

[NotATether]

private key 5vUtxFj43b4BM6t5dyXnLFEKLbXv8nB75fDFNRZLj7t7Vurvh address 3Nx***********************

Why is the address blacked out? Did you just encounter it like that or did you intentionally redact it?

How did you find out that it has 2.9 BTC in it without knowing the address?

[Alicatraz]

Thanks for your replies , I found It in an old USB stick , it does not belong to me , and I have no idea whose it is , I know the address , thats how I know it has 2.9 btc ,
I changed about 15 characters from the string preceding the address for obvious reasons ( just in case it was a private key of some sort of format )
its neither a compressed not uncompressed WIF p key , not a mini private key either , missing characters ? I am not sure , I literally copied everything and pasted it changing some characters.

[Charles-Tim]

its neither a compressed not uncompressed WIF p key , not a mini private key either , missing characters ? I am not sure , I literally copied everything and pasted it changing some characters.

If the private key has 51 characters, it should be a valid private key.

It is uncompressed as it starts from 5, compressed private key will start from K or L and have 52 characters. Mini private key have shorter characters.

That is uncompressed private key, it should have 51 characters.

[LoyceV]

I found It in an old USB stick

How old? If the address was funded before August 2017, you can be certain it's multisig and not Segwit.

[PawGo]

That does look like a bitcoin private key except that it is missing 2 characters since the correct length of an uncompressed private key is 51 not 49.
How did you "find" this anyway? Because if it really did contain 2.9 BTC you wouldn't just come across it. This looks like a fake thing since I checked and no combination of these characters with 2 at different positions could be a valid private key either.

Apart of fact that it looks like uncompressed and it must be compressed key for 3... address, "5v" is also incorrect beginning of uncompressed WIF because it could be only 5H/J/K.

OP: What address you are talking about? 3Nxdf6JrWiip45DpL9tJPGd9ym2CMmjJuy, 3Nx7d2aR1vULYi4rfbnB2ccD4nMsv7RFcN, 3NxSCBshZVqBTZVMkwVxphxKyn3NqpEkQ6 ? They are not so old.

[Charles-Tim]

Apart of fact that it looks like uncompressed and it must be compressed key for 3... address, "5v" is also incorrect beginning of uncompressed WIF because it could be only 5H/J/K.

You are right. But for this not to be misleading, it should be 5H/5J/5K. Or better this way, 5H, 5J or 5K.

[pooya87]

Apart of fact that it looks like uncompressed and it must be compressed key for 3... address,

The private key could be one out of one or more keys used in a legacy P2SH redeem script (eg. in a timelock or a multisig script) so it can be either compressed or uncompressed. Even if this corresponds to a P2SH-P2WPKH script it still could be a non-standard uncompressed key.