Question: Based on what, a form of polyalphabetic substitution uses a series of interwoven Caesar ciphers for encrypting alphabetic text?
Context: Disemvoweling, disemvowelling (see doubled "L"), or disemvowelment of a piece of alphabetic text is rewriting it with all the vowel letters removed.  This original sentence: A cryptogram is a type of puzzle that consists of a short piece of encrypted text.  Generally the cipher used to encrypt the text is simple enough that the cryptogram can be solved by hand.  Frequently used are substitution ciphers where each letter is replaced by a different letter or number.  To solve the puzzle, one must recover the original lettering.  Though once used in more serious applications, they are now mainly printed for entertainment in newspapers and magazines. The Alberti cipher disk, also called formula, is a cipher disc which was described by Leon Battista Alberti in his treatise De Cifris of 1467.  The device embodies the first example of polyalphabetic substitution with mixed alphabets and variable period, and is made up of two concentric disks, attached by a common pin, which can rotate one with respect to the other. The Standard Arabic Technical Transliteration System, commonly referred to by its acronym SATTS, is a system for writing and transmitting Arabic language text using the one-for-one substitution of ASCII-range characters for the letters of the Arabic alphabet.  Unlike more common systems for transliterating Arabic, SATTS does not provide the reader with any more phonetic information than standard Arabic orthography does; that is, it provides the bare Arabic alphabetic spelling with no notation of short vowels, doubled consonants, etc.  In other words, it is intended as a transliteration tool for Arabic linguists, and is of limited use to those who do not know Arabic. A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets.  The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case.  The Enigma machine is more complex but still fundamentally a polyalphabetic substitution cipher. In classical cryptography, the running key cipher is a type of polyalphabetic substitution cipher in which a text, typically from a book, is used to provide a very long keystream.  Usually, the book to be used would be agreed ahead of time, while the passage to be used would be chosen randomly for each message and secretly indicated somewhere in the message. In cryptanalysis, Kasiski examination (also referred to as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigenère cipher.  It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846. The Vigenère cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers based on the letters of a keyword.  It is a form of polyalphabetic substitution. The grill method (Polish: "metoda rusztu" ), in cryptology, was a method used chiefly early on, before the advent of the cyclometer, by the mathematician-cryptologists of the Polish Cipher Bureau ("Biuro Szyfrów") in decrypting German Enigma machine ciphers.  The Enigma rotor cipher machine changes plaintext characters into cipher text using a different permutation for each character, and so implements a polyalphabetic substitution cipher. Sukhotin's algorithm (introduced by Boris V. Sukhotin) is a statistical classification algorithm for classifying characters in a text as vowels or consonants.  It may also be of use in some of substitution ciphers and has been considered in deciphering the Voynich manuscript, though one problem is to agree on the set of symbols the manuscript is written in.
Answer: letters of a keyword