The Martin 193 was a design for a giant cargo transport seaplane that was conceived in 1942 as part of the "Sky Freighter" concept for colossal flying boats that could carry large loads of troops and freight across the Atlantic Ocean in response to the sinking of Allied merchant ships by U-boats.. It was basically a 40% enlargement of the Martin JRM Mars, weighing 250,000 pounds …

Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext.The keys may be identical, or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information …