user34110: Private keys are 256 bits (32-bytes) long, according to bitcoin wiki:
https://en.bitcoin.it/wiki/Private_key
Diamond Circle, an Australian startup, sent me a pair of bitcoin address and its private key. Blockchain.info shows that the money is still in the given address.
The problem is that the private key is 64-bytes long. It's base-64 encoded evident by the trailing ==
Since it's not in WIF, I wonder how to import it. Has anyone seen 64bit private keys before?

user34132: Taking into account that 64bytes keys are probably seed keys in bip32 format you might need to derive the key first. I modified the code to reflect that 
npm install coinstring hdkey
node 
var HDKey = require('hdkey')
var cs = require('coinstring')

// This is your base64 key 
var seed = 'oMQqnDrGq/K6aplGroOvGPUb8cn6fazEySUTzE3QFYNDQcd13NTA+sc1R8VmLYGp6TYaCqxgSnOjIb2RA7zorw=='
var hdkey = HDKey.fromMasterSeed(new Buffer(seed, 'base64'))

var hex = hdkey.privateKey
var version = 0x80; //Bitcoin private key
console.log(cs.encode(hex, version)) 

It should give you the familiar WIF format private key.
5HyfJgfUm7WVgUrLuo9uwtJR6ME7MYfGRhK2aeckZRooSKYGXP8

34110: <p>Private keys are 256 bits (32-bytes) long, according to bitcoin wiki:
<a href="https://en.bitcoin.it/wiki/Private_key" rel="nofollow">https://en.bitcoin.it/wiki/Private_key</a></p>

<p>Diamond Circle, an Australian startup, sent me a pair of bitcoin address and its private key. Blockchain.info shows that the money is still in the given address.</p>

<p>The problem is that the private key is <strong>64-bytes</strong> long. It's base-64 encoded evident by the trailing ==</p>

<p>Since it's not in WIF, I wonder how to import it. Has anyone seen 64bit private keys before?</p>
 34132: <p>Taking into account that 64bytes keys are probably seed keys in bip32 format you might need to derive the key first. I modified the code to reflect that </p>

<pre><code>npm install coinstring hdkey
node 
var HDKey = require('hdkey')
var cs = require('coinstring')

// This is your base64 key 
var seed = 'oMQqnDrGq/K6aplGroOvGPUb8cn6fazEySUTzE3QFYNDQcd13NTA+sc1R8VmLYGp6TYaCqxgSnOjIb2RA7zorw=='
var hdkey = HDKey.fromMasterSeed(new Buffer(seed, 'base64'))

var hex = hdkey.privateKey
var version = 0x80; //Bitcoin private key
console.log(cs.encode(hex, version)) 
</code></pre>

<p>It should give you the familiar WIF format private key.</p>

<p>5HyfJgfUm7WVgUrLuo9uwtJR6ME7MYfGRhK2aeckZRooSKYGXP8</p>
