Triliteral Cipher

Question 1

What is a Triliteral cipher? (Definition)

Answer

A triliteral cipher (also called ternary or trifid) is a substitution cipher where each letter or symbol in the plaintext message is replaced by a triplet of symbols.

The term triliteral means that the cipher uses three elements (3 letters) to represent a unit of information.

Question 2

How to encrypt using Triliteral cipher?

Answer

To encode with a triliteral cipher, follow these steps:

— Define a substitution alphabet (see below) so that each letter of the plaintext is associated with a triplet of symbols.

— Encode DCODE with the alphabet A=AAA, B=AAB, C=AAC, D=ABA, etc.

— Replace each letter of the plaintext with its corresponding triplet.

— The message is encrypted as: ABA AAC BBC ABA ABB

Question 3

What are the most common triliteral alphabets?

Answer

Base 3 (space ⌴ at the end = CCC):

A	AAA	B	AAB	C	AAC	D	ABA	E	ABB	F	ABC	G	ACA	H	ACB	I	ACC
J	BAA	K	BAB	L	BAC	M	BBA	N	BBB	O	BBC	P	BCA	Q	BCB	R	BCC
S	CAA	T	CAB	U	CAC	V	CBA	W	CBB	X	CBC	Y	CCA	Z	CCB	⌴	CCC

Base 3 (space ⌴ at the beginning = AAA):

⌴	AAA	A	AAB	B	AAC	C	ABA	D	ABB	E	ABC	F	ACA	G	ACB	H	ACC
I	BAA	J	BAB	K	BAC	L	BBA	M	BBB	N	BBC	O	BCA	P	BCB	Q	BCC
R	CAA	S	CAB	T	CAC	U	CBA	V	CBB	W	BCB	X	CCA	Y	CCB	Z	CCC

Frederici:

A	AAB	B	AAC	C	ABA	D	ABB	E	ABC	F	ACA	G	ACB	H	ACC	I	BBA
J	BBA	K	BBC	L	BAB	M	BAA	N	BAC	O	BCB	P	BCA	Q	BCC	R	CCA
S	CCB	T	CAC	U	CAA	V	CAA	W	CAB	X	CBC	Y	CBA	Z	CBB

Cardan:

A	AAC	B	AAB	C	ACA	D	ACC	E	ACB	F	ABA	G	ABC	H	CAC	I	ABB
J	ABB	K	CAB	L	CAA	M	CCA	N	CCB	O	CBA	P	CBC	Q	CBB	R	BAA
S	CCC	T	BAC	U	BAB	V	BAB	W	BAB	X	BCA	Y	BCC	Z	BCB

Vigenere:

A	BBA	B	BAA	C	BAC	D	AAA	E	AAC	F	AAB	G	ACA	H	ACC	I	ACB
J	ACB	K	ABA	L	ABC	M	ABB	N	CCC	O	CCA	P	CCB	Q	CAA	R	CAC
S	CAB	T	CBA	U	CBC	V	CBC	W	CBC	X	CBB	Y	BBB	Z	BCB

Wilkins:

A	AAA	B	AAB	C	AAC	D	BAA	E	BBA	F	BBB	G	BBC	H	CAA	I	CCA
J	CCA	K	CCB	L	CCC	M	ABA	N	ABB	O	ABC	P	ACA	Q	ACB	R	ACC
S	BCA	T	BCB	U	BCC	V	BCC	W	BAB	X	CBA	Y	CBB	Z	CBC

Some sources present Wilkins' alphabet with different trigrams.

Question 4

How to decrypt Triliteral cipher?

Answer

To decode a triliteral ciphertext:

— Segment the ciphertext into triplets of 3 characters

Example: The message to be decrypted ABAAACBBCABAABB is segmented into ABA,AAC,BBC,ABA,ABB

— Replace each triplet with its corresponding letter in the substitution alphabet to reconstruct the plaintext

Example: Using the alphabet A=AAA, B=AAB, C=AAC, D=ABA, etc. The plaintext is DCODE.

Question 5

How to decipher Triliteral without knowing the alphabet?

Answer

If the substitution alphabet is unknown, it is possible to transform the ciphertext into a monoalphabetic substitution by grouping triplets and analyzing their frequency.

The ciphertext then becomes a monoalphabetic substitution, and if the ciphertext is long enough, decryption is possible.

Question 6

How to recognize triliteral ciphertext?

Answer

The ciphered message has 3 distinct characters equally distributed. It is usually the 3 letters A, B and C but it can be 3 numbers, or 3 different things.

Like a Bacon cipher, it is possible to hide a Triliteral cipher in a text, for example by alternating 3 fonts, or variations of letters: uppercase, lowercase, bold, italic, underlined, etc.

All notions of triplet, number 3, triple, words trifid, triliteral, tricode, triletter, tridigital, etc. are clues.

Question 7

What are the 27 combinations of the Triliteral Alphabet?

Answer

The list of permutations with repetition of 3 characters A, B and C is: AAA, AAB, AAC, ABA, ABB, ABC, ACA, ACB, ACC, BAA, BAB, BAC, BBA, BBB, BBC, BCA, BCB, BCC, CAA, CAB, CAC, CBA, CBB, CBC, CCA, CCB, CCC

These combinations allow for the representation of up to 27 different characters.

Question 8

When was the Triliteral cipher invented?

Answer

The first triliteral alphabet appeared between 1550 and 1650.

Triliteral Cipher