In digital currency systems, a user’s private key determines the ownership of the currency. With the increasing popularity of central bank digital currency (CBDC), secure protections for users’ private signing keys become more urgent. Compared with transactions between individuals, transactions between corporations have lower frequency but larger amounts, demanding even higher security of the private key. In recent years, scholars have proposed a series of hardware-based private key protection schemes. However, numerous successful attacks on secure hardware have demonstrated that merely relying on hardware protection is insufficient. Program obfuscation is an effective approach for protecting private keys. Therefore, this paper proposes an obfuscatable encrypted SM2 signature scheme and its obfuscator, aiming at enhancing the security of private signing keys in China’s CBDC transactions between corporations. The correctness and security of the proposed scheme are formally proven, and a series of experimental evaluations are conducted on different mainstream devices. The results show that the proposed scheme improves the security of the user’s private signing key with relatively low computational overhead, thus obtaining high availability in China’s CBDC systems.