<s>
In	O
classical	O
cryptography	O
,	O
the	O
bifid	B-Algorithm
cipher	I-Algorithm
is	O
a	O
cipher	O
which	O
combines	O
the	O
Polybius	O
square	O
with	O
transposition	B-Algorithm
,	O
and	O
uses	O
fractionation	O
to	O
achieve	O
diffusion	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
each	O
ciphertext	O
character	O
depends	O
on	O
two	O
plaintext	O
characters	O
,	O
so	O
the	O
bifid	O
is	O
a	O
digraphic	O
cipher	O
,	O
like	O
the	O
Playfair	B-Algorithm
cipher	I-Algorithm
.	O
</s>
