user27433: When I use blockchain.info tools or bitcointoolkit.info tools 
to convert an address, such as 1MCNpVGDY7BGjJyWZL5FJZiaVkQEiuxy8H
to a hash 160 public key : I get dd894dfc0f473c44cc983b5dd462bc1b393f7498
However, if i convert 3MtPk2kf61VepUfwgRjqjC5WeGgxE4rRPS
i get the SAME 160 hash address ie dd894dfc0f473c44cc983b5dd462bc1b393f7498
I am baffled by this. I thought a hash 160 should UNIQUELY convert between it and the Address and back ??? 
I also found other address that convert back fro hash160 to the wrong address....
thanks for any clarification.....
9a278585c51203bca9f0e5c107814ecef6f2aa12

user24925: Both of those are correct decoding, the difference is the base58check version byte. 

1MCNpVGDY7BGjJyWZL5FJZiaVkQEiuxy8H has a version byte of 0x01 for P2PKH
3MtPk2kf61VepUfwgRjqjC5WeGgxE4rRPS has a version byte of 0x05 for P2SH

Due to it being a hash, only one of these is typically going to have a valid destination, either a pubkey (P2PKH) or a script (P2SH). If money has been sent to both version bytes of the same hash it is very likely that one amount has been lost. 

27433: <p>When I use blockchain.info tools or bitcointoolkit.info tools </p>

<p>to convert an address, such as 1MCNpVGDY7BGjJyWZL5FJZiaVkQEiuxy8H
to a hash 160 public key : I get dd894dfc0f473c44cc983b5dd462bc1b393f7498</p>

<p>However, if i convert 3MtPk2kf61VepUfwgRjqjC5WeGgxE4rRPS
i get the SAME 160 hash address ie dd894dfc0f473c44cc983b5dd462bc1b393f7498</p>

<p>I am baffled by this. I thought a hash 160 should UNIQUELY convert between it and the Address and back ??? </p>

<p>I also found other address that convert back fro hash160 to the wrong address....</p>

<p>thanks for any clarification.....</p>

<p>9a278585c51203bca9f0e5c107814ecef6f2aa12</p>
 24925: <p>Both of those are correct decoding, the difference is the base58check version byte. </p>

<ul>
<li><p>1MCNpVGDY7BGjJyWZL5FJZiaVkQEiuxy8H has a version byte of <code>0x01</code> for P2PKH</p></li>
<li><p>3MtPk2kf61VepUfwgRjqjC5WeGgxE4rRPS has a version byte of <code>0x05</code> for P2SH</p></li>
</ul>

<p>Due to it being a hash, only one of these is typically going to have a valid destination, either a pubkey (P2PKH) or a script (P2SH). If money has been sent to both version bytes of the same hash it is very likely that one amount has been lost. </p>
