A new method of optical cryptography using dark-bright soliton conversion control within a modified add/drop optical filter is proposed. A pair of optical keys is randomly generated and transmitted into the transmission line, where finally the corrected keys between Alice (sender) and Bob (receiver) can be retrieved. In principle, the coincidence (orthogonal) dark-bright soliton pair has shown promising behaviors, especially when they propagate into the π/2 phase shifter, i.e. beamsplitter, the shift in phase of π/2 between dark and bright solitons is occurred and separated. Such behaviors can be used to form the orthogonal light modes (solitons), which are useful for cryptographic application, where in this case the long-distance cryptography can be easily managed. We have derived and presented a new concept of multi-orthogonal solitons generated by using dark-bright soliton pulses within the modified add/drop optical filter, which is known as a PANDA ring resonator. By using the dark-bright soliton conversion control, the obtained output of the dynamic states can be used to randomly form the multi-orthogonal soliton pairs, which can be available for computer and communication security applications, especially for long-distance link.