<p>Bitcoin public keys are simply points on the elliptic curve secp256k1. Each point has an x and y value, and an (uncompressed) public key is encoded with the <code>0x04</code> to show that it is an uncompressed public key as opposed to a compressed or other, and then followed by the x and y coordinates, each 32 bytes long. The <code>0x04</code> is just a prefix, the key itself is the point on the curve. </p>

<p>There are 2 interpretations of first and last keys that I can see. Either you mean the 'first' key is the one corresponding to a private key of 0x01, or the key with the smallest x and y values. secp256k1 is the curve y<sup>2</sup> = x<sup>3</sup> + 7, so any x and y values that satisfy this equation (modulo the prime p = <code>FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F</code> <a href="https://en.bitcoin.it/wiki/Secp256k1" rel="nofollow noreferrer">[ref]</a>) is a valid point on the curve and thus public key. So x=0, y=1 would not be a valid point, because it doesn't satisfy that equation.</p>

CC BY-SA 3.0
2017-08-22T06:49:05.833Z
2017-08-22T06:49:05.833Z
meshcollider
<blockquote>
  <p>i was trying to see howmany public keys are available</p>
</blockquote>

<p>~ 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 may be a couple less :)</p>

<blockquote>
  <p>the complete publickey with 04 bit on it</p>
</blockquote>

<p>do not mix the public key and standatized written form of it</p>

CC BY-SA 3.0
2017-08-21T11:03:34.820Z
I think you should include where that number came from, perhaps explaining what a public key actually is, and what the 0x04 means
meshcollider
CC BY-SA 3.0
2017-08-21T14:11:58.537Z
Thats what im trying to figure out, what role the 04 comes into play
Rob
CC BY-SA 3.0
2017-08-21T14:13:24.740Z
So would it be something like this for the X & Y points?  What would the last public key look like?     04FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 ?
Rob
CC BY-SA 3.0
2017-08-21T20:04:24.993Z
'last' private key is FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364140 'last' public key is 0479BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798B7C52588D95C3B9AA25B0403F1EEF75702E84BB7597AABE663B82F6F04EF2777
amaclin
CC BY-SA 3.0
2017-08-21T21:49:57.753Z
I know that that public key goes with that last private key, but numberwise, the public keys go higher then that, im trying to figure out what the #1 public would be be in hex format, something like this 0400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001  this gives me a good address of 1JHkucsiQt3WizTfd2r1b9sGeT6cUBXPii  but is it valid on the blockchain?
Rob
CC BY-SA 3.0
2017-08-22T06:18:45.983Z
Please update the question and answer with the new information rather than using the comments section :)
meshcollider
CC BY-SA 3.0
2017-08-21T09:09:18.880Z
2017-08-21T09:09:18.880Z
amaclin
<p>What does the public key address start at?  and end?  is that available?
i was trying to see howmany public keys are available,  and it would be cool to know at what number it starts and ends.  the complete publickey with 04 bit on it</p>

<pubnub>
Public key Start?
Rob
# Public key Start?

(Asked by: username_0 on 2017-08-21)

What does the public key address start at? and end? is that available?
i was trying to see howmany public keys are available, and it would be cool to know at what number it starts and ends. the complete publickey with 04 bit on it

**Tags:** pubnub


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## 2 answers

### Answer by username_1 on 2017-08-22. Score: 1 | Accepted answer

Bitcoin public keys are simply points on the elliptic curve secp256k1. Each point has an x and y value, and an (uncompressed) public key is encoded with the `0x04` to show that it is an uncompressed public key as opposed to a compressed or other, and then followed by the x and y coordinates, each 32 bytes long. The `0x04` is just a prefix, the key itself is the point on the curve.

There are 2 interpretations of first and last keys that I can see. Either you mean the 'first' key is the one corresponding to a private key of 0x01, or the key with the smallest x and y values. secp256k1 is the curve y2 = x3 + 7, so any x and y values that satisfy this equation (modulo the prime p = `FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F` [[ref]](https://en.bitcoin.it/wiki/Secp256k1)) is a valid point on the curve and thus public key. So x=0, y=1 would not be a valid point, because it doesn't satisfy that equation.


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### Answer by username_2 on 2017-08-21. Score: 0

> i was trying to see howmany public keys are available

~ 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 may be a couple less :)

> the complete publickey with 04 bit on it

do not mix the public key and standatized written form of it

> **Comments:**
> **username_1**: I think you should include where that number came from, perhaps explaining what a public key actually is, and what the 0x04 means  
> **username_0**: Thats what im trying to figure out, what role the 04 comes into play  
> **username_0**: So would it be something like this for the X & Y points?  What would the last public key look like?     04FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 ?  
> **username_2**: 'last' private key is FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364140 'last' public key is 0479BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798B7C52588D95C3B9AA25B0403F1EEF75702E84BB7597AABE663B82F6F04EF2777  
> **username_0**: I know that that public key goes with that last private key, but numberwise, the public keys go higher then that, im trying to figure out what the #1 public would be be in hex format, something like this 0400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001  this gives me a good address of 1JHkucsiQt3WizTfd2r1b9sGeT6cUBXPii  but is it valid on the blockchain?  
> **username_1**: Please update the question and answer with the new information rather than using the comments section :)  

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