This cipher is a Vigenre Cipher with a twist. This cryptosystem operates on bytes (8-bits): for an alphabet of 256 values (0255). Text will be represented as ASCII (A is represented by hex 0x41, etc.). Instead of shift, Exclusive OR (XOR) is used. Because of this, encryption and decryption are the same operation.

def encode(text): return base64.b64encode(text) def decode(text): return base64.b64decode(text) def encrypt(cleartext, key): to_return = bytearray(len(cleartext)) for i in range(len(cleartext)): to_return[i] = cleartext[i] ^ key[i % len(key)] return bytes(to_return)

Here is your encrypted ciphertext (note that the whitespace is not important):

DhJSCjZLBBsAOx9PeCY/Cg9SMyYZCBwAaUskAEl9RUE6CCRFT1 xHGwQWUgM8SxgdEnMGBBMJcxIOB0ckBBMZRzIHDhwAIAIFF0cy SyYXFT4KD01tGw4NFwlpSzYXCz9HQRcGMANBHQFzHhJSDj0fBA AENhsVAUc+DhIBBjQOElIBIQQMUgZzGBEXBDoNCBFHFA4THwY9 SxMTAzoEQQYIJA4TXEcABEEFAnMDAAQCcwpBEQgmBRUXFSMKEw ZHPAVBBg82Sw4GDzYZQQEONw5NUhA7BEYBRycCEV8TMhsRGwk0 Sw4HE3MfCRdHPg4SAQY0DhJcRxYdBAAePAUEUhMqGwQBRzJLFR 0SMANBFg41DQQAAj0fDQtLcxgOUh48HkEVAidLFR1HOAUOBUcn AwRSFTsSFRoKcwQHUh48HhNSBDweDwYCIRsAABN9SygGQCBLEg YVMgUGFwsqSwgcEzoGAAYCfUsoUgE2Dg1SBiBLCBRHGksKHAgk SwkbCnMYDlIQNgcNXEcaH0YBRzJLERsTKksJF0c7ChJSBnMMCA ALNRkIFwk3R0EQEidLFRoGJ0wSUhA7EkE7RzcCEhMAIQ4EUhA6 HwlSHjweTVIqIUVBMws2EwAcAzYZTVIFNggABxQ2SyhVCnMCD1 ILPB0EUhA6HwlSBnMIDgUIIQAEAEc8DUEBCCEfElIGPQ9BBQJ0 HQRSCTYdBABHNh0EHEc+DhVcbRseBhpHEgcECgY9DwQAXXM8BB 4Lf0sAHgs8HEEfAnMfDlIFJhJBCwgmSwAcCCcDBABHIwIPBkcy BQVSLnQHDVITNgcNUh48HkEFDypLGB0SdBkEUhAhBA8VSVkjBB 4CPVFBPgInTBJcbRseBhpHEgcECgY9DwQAXXMuGRECPwcEHBN9 YTomDzYSQRUCJ0sUAkcyBQVSDzYKBVITPEsVGgJzCQAASXMqEl ITOw4YUgghDwQAS3MqDRMJcxgIBhRzCA4fFz8OFRcLKksSGws2 BRUeHn9LCBxHMksFEx02S0xSDzIdCBwAcwgOHwJzHw5SBnMZBB MLOhgABg48BTx4LTwKD1IkPwoTGQJpSygcRzAKEhdHKgQUUhA2 GQRSEDwFBRcVOgUGXkcnAwAGQCBLFhoGJ0sHHg4hHwgcAHMHDh 0MIEsNGww2RWszCzIFQSYSIQIPFV1zMA0dEjcHGC9HGw4NFwly YSsdBj1LIh4GIQAESEcIGA0bADsfDQtHNgYDExUhChIBAjdHQR MUcwMIAUcgAw4HE3MDAAFHNxkABQlzChUGAj0fCB0Jcx8OUhM7 DgwvRxIHABxGWSMEHgI9UUErAiBHQTMLMgVeeCY/Cg9SMyYZCB wAaUs6FQInGEEHF3MKDxZHNQoCFxRzAwQAOnM8CQtHNwRBCwgm SxUaDj0AQQsIJhlBNQIhBgAcRzAEFBwTNhkRExUnSwkTFHMKQR UOIQcHAA42BQVNbRsODRcJaUsoBkAgSwsHFCdLAFIUJx4RGwNz AQ4ZAn1LJR0JdB9BBQghGRhSBjEEFAZHOh9PeCY/Cg9SMyYZCB wAaUsvHUtzBQ5eRz0ETVIJPEdBHAh/SxUXCz9LDBdJWSMEHgI9 UUElAj8HTVICMggJUgg1SwkbFHMGBAEUMgwEAUcxDgYbCSBLFh sTO0sVGgJzGAAfAnMNCAQCcwcEBhM2GRJcRxBGKF8rfidMK0lz OA5SLnMYFAEXNggVUhM7ChVSJDoHDQtHPh4SBkcxDkEGDzZLDx MKNksOFEc7AhJSBj4EExdJWTAjC0cnAwgBRyMECBwTf0srHQY9 R0EiAicOE1IvOgcVHQlzCg8WRxkECRxHEAoIAAkwGQ4BFHMDAA QCcwkEFRI9SxUdRzAKFREPcwQPL20SBwAcRwceExsJNFFBMBIn SxUaBidMElIOPhsOARQ6CQ0XSXM/CRdHFA4THwY9GEETFTZLCB wUJxkUERM2D0EGCHMeEhdHNQIXF0chCg8WCD5LDRcTJw4TAUcy H0EGDzZLEgYGIR9BHQFzDhcXFSpLDBcUIAoGF0lZIwQeAj1RQS UCPwdNUhM7AhJSBT8EChdHNwQEAQl0H094LyYMCVImPw4ZEwk3 DhNIRx8EFxdHJAINHkc+CgoXRzJLDBMJcw8OUhQnGQAcADZLFR oOPQwSXkcaSxIHFyMEEhdJWSoNEwlzPxQADj0MW1IuPUsVGg4g SwITFDZFT1xJcycOBAJzARQBE3MHDgETcywEAAoyBRhSEzsOQQ UPPAcEUgU/BA4WHnMcAABGWTApF0chHhIaAiBLDhQBf0sDExU0 Ag8VRzoFFR1HGx4GGkcyBQVSBDIeEhsJNEsJGwpzHw5SFCMCDR 5HJwMEUhc6BRUBRzsOQRoGIEsLBxQnSwMdEjQDFVIIPUspFws2 BU9SLTwDD15HAw4VFxVzCg8WRxkEABxHIR4SGkc8DQdSBjUfBA BHOwIMUgY9D0E6EjQDTVIVNgoNGxQ6BQZSEDsKFVIPMhhBGgYj GwQcAjdHQRMXPAcOFQ4gDhJSBj0PQRYGIAMEAUc8DQdSBjUfBA BHJwMEHzpZIxQVD3MqDRcfMgUFFxVpSywLRxQEBV5HKgQUUgM6 D0EbE31LOB0ScwEUARNzDwQUAjIfBBZHHQobGxQ+SxYbEztLAF IEIQQSARA8GQVSFyY=

I have found the key length is 5. Please help me to find the key.