What is Coincidence Testing?

For an explanation of what this program is all about, read this article.

Enter your polyalphabetic ciphertext below and click "GO". The program will return a table of auto correlation coeficients for various possible key lengths. The most likely keys are those with the highest values. If you see high values for multiples of some key length, such as for key lengths 7, 14, 21, 35, and so on, the most likely key length is the smallest one, which in this example is 7.

The ciphertext must contain only letters and spaces, no punctuation marks. If you would like to see a sample of how it works, here's a polyalphabetic cipher with a key length of 4. You may cut and paste it into the ciphertext form below and see how the program detects the correct key length.

      UJHTM CLRPH VMMGQ GFKDQ BPRPE ODRJN LZFJH VFKQX
      IKVEO ELIOV KSVUH WVTUS VPGIE DBLVI HYOMH QQVJE
      SFHRT VKIQG DWBPW VZYKS JPKEC KWXIG ZMMFH VOGVW
      CGBSO FVEZV KEUKD QOCGX ICWMT DHGBW VIJYL PMJDZ
      FPRXI KQKUQ GSXKW LUJHQ JNLZF JHVFC OSOGZ MUJPC
      PNGWJ UWISY KSJUD PTQPC IQXWF MHIQG UAFMH IQPRW
      FTYEO VVMIC WIUJH QJJDZ FQQIG TLIOF DHPIB ITKZS
      VNGWP QQISJ DZFQO HQGST FTWLB PWLFT HWUQI GSGDX
      JQQXP IHXIG ULFCW PFCVX VPGIS UWEOF VQFCQ HICVW
      FPVIF PRYHJ WSMGD ZFOHE MQQIX JHRJC PMOOB HBTNQ
      PQGWJ JDZFF HGJFH HUQVX BTWEL KQHPH GMBTB MUODC