The plaintext message "meet me at sci crypt to discuss it more" is arranged in a rectangular form, and any trailing blanks are filled with "null" characters of "x" :
MEETMEAT
SCICRYPT
TODISCUS
SITMOREX
The ciphertext is produced by reading off the letters column by column. A keyword or key phrase can be placed above the rectangle to determine the order that the columns will be read.
PIZZAPIE
MEETMEAT
SCICRYPT
TODISCUS
SITMOREX
In this case the key will be "pizza pie" will be used, and the letters of the keyword will be converted to the numerals 1 to 8 based upon the relative positions of each letter in the alphabet. The "A" in the key comes first in the alphabet, so it will be set to "1", the "E" comes next, so it will be given the numeral "2", and so on. The letters "I", "P", and "Z" are repeated, so they will be assigned consecutive numbers in alphabetical order, from left to right. So the first "I" in "pizza" becomes 3, and the second "I" in "pie" becomes "4", giving:
53781642
MEETMEAT
SCICRYPT
TODISCUS
SITMOREX
The ciphertext is produced by reading off the letters by the columns in numerical order. The result is:
MRSO TTSX ECOI APUE MSTS EYCR EIDT TCIM
Usually the ciphertext is rearranged into groups of five to conceal any information about the size or the rectangle:
MRSOT TSXEC OIAPU EMSTS EYCRE IDTTC IM
The same plaintext could have been formed into this rectangle, could have used the keyword "suck":
SUCK
3412
MEET
MEAT
SCIC
RYPT
TODI
SCUS
SITM
OREX
With the resulting ciphertext:
EAIPDUTE TTCTISMX MMSRTSSO EECYOCIR
And rearranging to groups of five:
EAIPD UTETT CTISM XMMSR TSSOE ECYOC IR
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