## CRYPTOGRAPHY: THE COMMUNICATION MEANS BETWEEN CUBA AND ITS SPIES
The recent captured of more than 12 Cuban spies have shown the way that they communicate with the DGI in Cuba. The basic method is called Cryptography, and Cuba's uses the method developed in the 1970s, referred to as symmetric encryption, secret-key, or single key encryption. There are three important encryption algorithms: DES, triple DES, and AES. The encryption used by Cuba's intelligence has five ingredients: · Plaintext: This is the original message or data that is fed into the algorithm as input · Encryption algorithm: The encryption algorithm performs various substitutions and transformations on the plaintext · Secret key: The secret key is also input to the algorithm. The exact substitutions and transformations performed by the algorithm depend on the key · Ciphertext: This is the scrambled message produced as output. It depends on the plaintext and the secret key. For a given message, two different keys will produce two different ciphertexts · Decryption algorithm: This is essentially the encryption algorithm run in reverse. It takes the ciphertext and the same secret key and produces the original plaintext. They use two basic important requirements: · A strong encryption algorithm. They use one that, at the beginning, the opponent who knows the algorithm and has access to one or more ciphertexts, are unable to decipher the ciphertext or figure out the key.It was difficult, at the earlier stages to decipher their messages. · Sender and receiver (Cuba and the agents here) must have obtained copies of the secret key in a secure fashion and keep the key secure. Once the US intelligence discover the key and knows the algorithm, all communication using this key is readable. The security of this encryption depends on the secrecy of the key, not the secrecy of the algorithm. That is, they need to keep only the key secret. With the use of this encryption, the principal security problem is maintaining the secrecy of the key. All their encryption algorithms are based on two general principles: substitution, in which each element in the plaintext (bit, letter, group of bits or letters) is mapped into another element, and transposition, in which elements in the plaintext are rearranged. They use multiple stages of substitutions and transpositions. Both sender and receiver use the same key. The system is symmetric. A block cipher processes the input one block of elements at a time, producing an output block for each input block. A stream cipher processes the input elements continuously, producing output one element at a time, as it goes along. The process of attempting to discover the plaintext or key is known as cryptanalysis. A summary follows. The Table summarizes the various types of cryptanalytic attacks or means to decipher Cuba's communication with its spies. The most difficult problem is presented when all that is available is the ciphertext only. ## Type of attack Known to CryptanalystCiphertext only Encryption algorithm Ciphertext to be decoded Known plaintext Encryption algorithm Ciphertext to be decoded One or more plaintext-ciphertext pairs formed with the secret key Chosen plaintext Encryption algorithm Ciphertext to be decoded Plaintext message chosen by cryptanalist, together with its corresponding ciphertext generated with the secret key Chosen ciphertext Encryption algorithm; Ciphertext to be decoded; Purporpoted ciphertext chosen by cryptanalist, together with its corresponding decrypted plaintext generated with the secret key Chosen Text Encryption algorithm; Ciphertext to be decoded; Plaintext message chosen by cryptanalist, together with its corresponding ciphertext generated with the secret key; Purported ciphertext chosen by cryptanalist, together with its corresponding decrypted plaintext generated with the secret key
Manuel Cereijo March 2002 Este y otros excelentes artículos del mismo AUTOR aparecen en la REVISTA GUARACABUYA con dirección electrónica de: www.amigospais-guaracabuya.org
Si usted no es miembro de nuestra lista de distribución y quiere agregarse favor de ir a:http://lists.guaracabuya.org/mailman/listinfo/lista y favor de seguir las instrucciones.
If you are not a member of our mailing list and wish to be included,
please go to the following link:http://lists.guaracabuya.org/mailman/listinfo/lista and follow the instructions. |