Methods and apparatus for branch instruction security

Aspects of the present disclosure relate to an apparatus. Instruction receiving circuitry receives, as part of a program flow, a branch instruction, said branch instruction identifying a function. Instruction authentication circuitry determines, based at least in part on the function, an instruction authentication value. The instruction authentication circuitry then combines the instruction authentication value with the branch instruction to produce an authenticatable branch instruction. Branch circuitry authenticates the authenticatable branch instruction based on a function authentication value. Responsive to a successful authentication of the authenticatable branch instruction, the branch circuitry executes a jump in the program flow to said function.