Also known as "One Key release". These are Shimano's first attempt at self-extracting crank bolts. I agree with the Ankle: remove the retaining ring with a pin spanner, then use a good quality, tight fitting hex key on a socket handle to break them loose. Remove them and replace them with standard bolts torqued to 30 ft-lbs.

Throw away the One-Key Release bolts. Unless they're torqued carefully, it's very hard to get the correct amount of torque with a 6mm hex key. Back when they came out, I saw many Shimano cranks ruined due to inadequate torque.

Here's what they look like new: