1. A system comprising: at least one hardware device processor; and a computer-readable storage medium storing executable instructions that, when executed, cause one or more of the at least one hardware device processor to: control a number of transmissions of secure data that is communicated between a secure trusted device and an unsecure untrusted device in a database management system, the data being communicated for database transaction processing in the secure trusted device, the number of transmissions being controlled by: receiving, from the untrusted device, an encrypted key value of a key and a representation of an index of a B-tree structure, the index comprising secure, encrypted index values, decrypting, at the trusted device, the key and one or more of the encrypted index values, and initiating a transmission, in response to the receiving, a pointer value that identifies a lookup position in the index for the key.