Proposed here is a secure image encryption scheme based on generalized Vigenere cipher and Meitei Lock Sequence (MLS) generated from standard hash functions. MLS is a unique random sequence of any length greater than 2 generated from a non-negative array having two or more elements. It is unique in the sense that no two arrays can generate the same sequence however close or similar the two arrays are. In other words, when there is any slight change in any of the input array, the generated MLS’s are drastically different. Also, the length of the sequence can be as infinitely long. These properties make MLS a good key string for a secure encryption scheme. SHA(Secure Hashing Algorithm) or any hash code generator has desirable feature which can be used for generation of MLS. In a hash code generator, it produces unique fixed length sequence from any input string, if there is any slight change in the input, the generated output will be totally different. This feature is made used of  in generating an MLS of any desired length for use in the proposed image  encryption scheme. Experimental results show that the proposed encryption scheme is a secure encryption scheme. The correlation coefficient between the original image and encrypted images are negligibly small indicating that there is no trace of original image information in the encrypted image. Also, the correlation coefficients between the original image and decrypted images with wrong passwords which are close to the encryption password are also negligibly small. These show the tightness of the key system in the encryption scheme.