它是在1978年由Merkel和Hellman提出的。它的主要思路是假定某人拥有大量物品，重量各不同。此人通过秘密地选择一部分物品并将它们放到背包中来加密消息。背包中的物品中重量是公开的，所有可能的物品也是公开的，但背包中的物品是保密的。附加一定的限制条件，给出重量，而要列出可能的物品，在计算上是不可实现的。背包问题是熟知的不可计算问题，背包体制以其加密，解密速度快而其人注目。但是，大多数一次背包体制均被破译了，因此现在很少有人使用它。

-It was in 1978, made by Merkel and Hellman. Its main idea is to assume that a person has a large number of items, weight, different. This person chose a secret portion of the goods by them into the backpack to encrypt the message. The weight of the items in the backpack was open, and all possible items that are open, but the backpack of the items are confidential. Additional restrictions on certain conditions, given the weight, but might want to list items in the calculation is not achieved. Knapsack problem is well-known non-computable problems, knapsack system, with its encryption and decryption speed and its a lot of attention. However, most systems were cracked a backpack, so now very few people use it.