Permeability is a key property governing fluid transport in geomaterials and plays an important role in subsurface energy technologies such as deep geothermal stimulation, geological CO? sequestration, and hydrogen storage. In low-permeability rocks, however, conventional permeability measurements such as the classical transient pulse-decay test can take days, making rapid and reliable characterization challenging. This research seeks to infer permeability from the early-time portion of transient pressure measurements using the Integral-Balance Method. The early-time pressure distribution within the rock specimen is first represented by an assumed profile function, and global mass conservation will be then enforced by integrating the governing equations over the evolving difusion front. This technique reduces the original system of partial differential equations describing the test to a system of ordinary differential equations, leading to a robust regression procedure for determining rock permeability from early-time pressure data. A laboratory test using Vermont serpentinite successfully validated the method. Further extension of the framework to field-scale diagnostic tests, such as pressure fall-off test, will also be discussed.