Apple's iMessage system has a cryptography flaw that allowed researchers to decrypt a photo stored in iCloud, the Washington Post reported on Sunday. The researchers, led by cryptography expert Matthew D. Green of Johns Hopkins University, wrote software that mimicked an Apple server and then targeted an encrypted photo stored on iCloud, the publication reported. They were able to obtain the decryption key by repeatedly guessing each of its 64 digits. When a correct digit was guessed, the phone let them know if it was correct. Further technical details were not available.