Mixed Unary Cryptography

A method to combine two ciphers A and B to encrypt a plaintext to a corresponding ciphertext where selected parts of the plaintext are encrypted with cipher A which offers augmented security through generating a ciphertext larger than the corresponding plaintext,

• and where the remaining parts of the plaintext will be encrypted with a “base” cipher B, which is generating a ciphertext of similar size to the corresponding plaintext,
• such that the user achieves a desired balance between the security of the augmented ciphertext and the burden of its augmented size,
• where the transmitter and the intended recipient of the encrypted message will both share the base cipher key, Kb, and the augmented cipher key, Ka,
• and where the transmitter will mark on the transmitted plain message M n sections designated to be encrypted with cipher A:
• P1, P2, . . . Pn,
• and where the transmitter notices the bit position ti on M of each selected plaintext message P1 for i=1, 2, . . . n,
• and where the transmitter prepares each section i of the n sections for encryption by adding from the left h bits used to indicate the value of ti, and adding one trailer bit to the right of section P1 such that for i=1, 2, . . . (n−1), the value of trailer bit will be 1, and for i=n the value of the trailer bit will be zero:
• P*i=[h bits indicating ti]∥Pi∥[trailer bit]
• then the transmitter will encrypt each of these n sections P*1, P*2, . . . P*n using the augmented-ciphertext cipher A, generating their corresponding ciphertext sections C1, C2, . . . Cn,
• Ci=α(P*1,Ka)
• where α represents encryption with cipher A, and where the size of these n ciphertexts is the same c=|Ci| for i=1, 2, . . . n,
• and where the transmitter will remove the selected n sections Pi for i=1, 2, . . . n from M and concatenate the left-over separated sections of M to a contiguous left-over message Ml,
• and where the transmitter will encrypt M, with the base cipher B using key Kb:
• Cl=β(MbKb)
• where β is the encryption function with cipher B, and where the transmitter will prepare the mixed ciphertext, Cm, by concatenating in order the n ciphertexts Ci for i=1, 2, . . . n, and then concatenating Ci:
• Cm=C1∥C2∥ . . . ∥Cn∥Cl
• next the transmitter transmits Cm to the intended recipient;
• the intended recipient will remove the c leftmost bits from Cm, namely Ci for i=1, then decrypt it to the corresponding P*i using Ka:
• P*i=α−1(Ci,Ka) . . . for i=1·2, . . . n
• where α−1 is the decryption operation of cipher A;
• then the recipient will decompose P*i to the leftmost h bits indicating ti, Pi, and the trailer bit;
• if the trailer bit is 1, then the recipient increments i→i+1 and repeats the extraction of c bits from what is left from Cm;
• for i=n the trailer bit is found to be zero, indicating to the recipient that all the n sections were removed from Cm and the leftover from Cm, is Cl, which then the recipients decrypts using Kb
• Ml=β−1(CbKb)
• where β−1 is the decryption function for cipher B;
• then the recipients interjects P1 for i=1 into M, at position ti, then increments i→(i+1), and interjects the next section in its indicated position, and so on for all the n sections,
• after interjecting the n sections in their indicated positions t1, t2, . . . tn, the left-over plaintext M, is being rebuilt to M, readable by the recipient.