Cryptocurrency is a digital currency with cryptographic security so that it is not easily to be faked. Recently cryptocurrency is widely used for transactions. Therefore, preserving its integrity and security is important. The technology underlying the digital currency is the Blockchain, as applied to Fawkescoin. But for securing the transaction, fawkescoin has a disadvantage when the fork occurs because it can provide opportunity to conduct double spending attack. To overcome this problem, Merkle tree proposed by applying DSA digital signatures. The application of DSA on Merkle tree is used to verify data without knowing the contents of the data. Based on the experiment results and analysis, the security of the proposed method can prevent fawkescoin against double spending attack on transactions when forking occurs than the previous method.