The Solfa cipher is a substitution cipher, but rather than using an alphabet to encode keys and cipher text, it uses musical notation. The encryption/decryption key is defined using a clef, a tonic, a mode and a rhythmic unit. The 4 elements mentioned can have the following values:
Like any symmetric cipher, a key is needed to encrypt the message, which will have to be shared with the intended recipients of the message. In this case, the key is in musical notation rather than a sequence of characters or bytes. The first staff of the page represents the key of the cipher, as the label clearly shows. The encryption key is composed of the four elements mentioned above: a treble clef, in C minor, using 1/8 as the rhythmic unit.
Each note is linked to a the seven pitches of the solfege, i.e. Do (D), Re (R), Mi (M), Fa (F), Sol (S), La (L) and Si (T). The “KEY-554” is only a randomly generated label and has no significance in the algorithm. With the key known, this puzzle becomes a chain of translations from musical notes to a list of tuple of tones and rhythms using the standard matrix below:
A = M,1
B = L,4
C = R,3
D = S,3
E = S,1
F = D,4
G = M,4
H = M,3
I = R,1
J = S,2
K = D,2
L = L,3
M = F,3
N = L,1
O = T,1
P = F,4
Q = F,2
R = D,3
S = F,1
T = D,1
U = T,3
V = T,4
W = S,4
X = M,2
Y = R,4
Z = R,2