Quantum cryptography and computercryptography are two branches of cryptography at the same age. Quantum cryptography based on the quantum mechanics can achieve unconditionally secure communications.
量子密码是与计算机密码处于同一时代的密码学分支，它以量子力学为基础，能实现无条件安全的保密通信。
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This article first analyzes the security of computer network, introduces basic technology that guarantee the security and emphasizes that cryptography is the core technology.
Information hiding is an interlaced subject, which is built on the basis of mathematics, modern cryptography, information processing theory, and computer applied techniques.