Abstract: Freeing memory safely with low performance overhead in a concurrent environment is described. An example method includes creating a reference count for each sub block in a global memory block, and each global memory block includes a plurality of sub blocks aged based on respective allocation time. A reference count for a first sub block is incremented when a thread operates a collection of data items and accesses the first sub block for a first time. Reference counts for the first sub block and a second sub block are lazily updated. Subsequently, the sub blocks are scanned through in the order of their age until a sub block with a non-zero reference count is encountered. Accordingly, one or more sub blocks whose corresponding reference counts are equal to zero are freed safely and with low performance overhead.

Abstract: Multi-control password changing includes initiating a password change cycle to change a target user's password, selecting a plurality of administrators to provide password part inputs, receiving password part inputs separately and confidentially from the plurality of administrators, generating a multi-control password comprised of multiple password part inputs, changing the target user's password to the multi-control password, and transmitting either the single multi-control password or multiple password parts each separately to target user.