user43677: Just created a new wallet using Bitcoin Core v0.15.1 (Windows x64), encrypted it with a password, and created one receiving address. The size of this wallet is 1 Mb.
In comparison, my old wallet, with about a dozen receiving addresses and transactions, encrypted using the password of the exact same length, is only 100 Kb.
I thought the 1 Mb is too large and suspicious. What could be the reason for this size? 

user208: The default size of the keypool was raised from 100 keys to 2x 1000 keys.
This was done in order to reduce the cases where recovery of a backup needs to decrypt the wallet to generate further keys.

43677: <p>Just created a new wallet using Bitcoin Core v0.15.1 (Windows x64), encrypted it with a password, and created one receiving address. The size of this wallet is 1 Mb.</p>

<p>In comparison, my old wallet, with about a dozen receiving addresses and transactions, encrypted using the password of the exact same length, is only 100 Kb.</p>

<p>I thought the 1 Mb is too large and suspicious. What could be the reason for this size? </p>
 208: <p>The default size of the keypool was raised from 100 keys to 2x 1000 keys.</p>

<p>This was done in order to reduce the cases where recovery of a backup needs to decrypt the wallet to generate further keys.</p>
