Is it possible to combine multi-sig and locktime? Is it possible to create a 1 of 2 multi-sig address in which only one of the keys is time-locked and the other can sign any time?
only one of the keys is time-locked


Keys aren't time-locked. Transactions are. However, Bitcoin now has an opcode for this purpose: OP_CHECKLOCKTIMEVERIFY.

Essentially, it forces the transaction to have a lock time further in the future than its argument, otherwise the transaction is invalid.

In your case, the script would look like this:

OP_IF &lt;this pubkey can spend at any time&gt; OP_CHECKSIG OP_ELSE &lt;block number&gt; OP_CHECKLOCKTIMEVERIFY OP_DROP &lt;this pubkey must wait until block number&gt; OP_CHECKSIG OP_ENDIF


The spend-anytime key can redeem the transaction with

&lt;Sig&gt; 1 &lt;above script&gt;


The other key can redeem with

&lt;Sig&gt; 0 &lt;above script&gt;


but only after the given block number.