arXiv:2610.34863v1 Announce Type: new Abstract: Secure convertible codes, introduced by Zhang and Rashmi, achieve secrecy capacity under a passive eavesdropper model in which an eavesdropper is allowed to access any $\ell$ symbols from the initial and final codewords. In this paper, we construct two families of access-optimal secure convertible codes. The first family of codes based on Maximum Rank Distance (MRD) codes is constructed for all parameters in the merge and split regimes and requires a large field size. The second family of codes, constructed using Generalized Reed-Solomon codes, uses smaller fields but is applicable only for certain parameters in the merge and split regimes.