A hidden shackle style lock is disclosed. The lock includes a substantially cylindrical housing having a top surface, a bottom surface, and a curved side surface. The lock also includes a first cavity on the bottom surface of the housing extending part way along a thickness of the housing, and a second cavity on the side surface intersecting with the first cavity. A hollow sleeve is slidably attached within the second cavity. The sleeve includes a first end face, a second end face, and a third cavity. The third cavity extends from the first end face to the second face and is substantially coaxial with the second cavity. A shackle having a first end and a second end is fixedly coupled to the first end face of the sleeve. The lock also includes an interchangeable core having a first locking mechanism and a second locking mechanism lockingly disposed within the third cavity, and coupled to the straight shackle. The interchangeable core is configured to operate the first locking mechanism to rotate the shackle, and operate the second locking mechanism to unlock the interchangeable core from the third cavity.