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* Update 07.3.md * Update 07.3.md * Update 07.6.md * fix few problems * Update 10.6 and 10.8 * Update 11.6 and 11.7 * fix some problems before Chap13 * add a dot
87 lines
2.5 KiB
Markdown
87 lines
2.5 KiB
Markdown
# 12.12 Go 中的密码学
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通过网络传输的数据必须加密，以防止被 hacker（黑客）读取或篡改，并且保证发出的数据和收到的数据检验和一致。
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鉴于 Go 母公司的业务，我们毫不惊讶地看到 Go 的标准库为该领域提供了超过 30 个的包：
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- `hash` 包：实现了 `adler32`、`crc32`、`crc64` 和 `fnv` 校验；
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- `crypto` 包：实现了其它的 hash 算法，比如 `md4`、`md5`、`sha1` 等。以及完整地实现了 `aes`、`blowfish`、`rc4`、`rsa`、`xtea` 等加密算法。
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下面的示例用 `sha1` 和 `md5` 计算并输出了一些校验值。
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示例 12.20 [hash_sha1.go](examples/chapter_12/hash_sha1.go)：
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```go
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// hash_sha1.go
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package main
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import (
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"fmt"
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"crypto/sha1"
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"io"
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"log"
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)
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func main() {
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hasher := sha1.New()
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io.WriteString(hasher, "test")
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b := []byte{}
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fmt.Printf("Result: %x\n", hasher.Sum(b))
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fmt.Printf("Result: %d\n", hasher.Sum(b))
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//
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hasher.Reset()
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data := []byte("We shall overcome!")
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n, err := hasher.Write(data)
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if n!=len(data) || err!=nil {
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log.Printf("Hash write error: %v / %v", n, err)
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}
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checksum := hasher.Sum(b)
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fmt.Printf("Result: %x\n", checksum)
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}
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```
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输出：
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```
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Result: a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
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Result: [169 74 143 229 204 177 155 166 28 76 8 115 211 145 233 135 152 47 187 211]
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Result: e2222bfc59850bbb00a722e764a555603bb59b2a
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```
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通过调用 `sha1.New()` 创建了一个新的 `hash.Hash` 对象，用来计算 SHA1 校验值。`Hash` 类型实际上是一个接口，它实现了 `io.Writer` 接口：
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```go
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type Hash interface {
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// Write (via the embedded io.Writer interface) adds more data to the running hash.
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// It never returns an error.
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io.Writer
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// Sum appends the current hash to b and returns the resulting slice.
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// It does not change the underlying hash state.
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Sum(b []byte) []byte
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// Reset resets the Hash to its initial state.
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Reset()
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// Size returns the number of bytes Sum will return.
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Size() int
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// BlockSize returns the hash's underlying block size.
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// The Write method must be able to accept any amount
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// of data, but it may operate more efficiently if all writes
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// are a multiple of the block size.
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BlockSize() int
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}
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```
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通过 io.WriteString 或 hasher.Write 将给定的 []byte 附加到当前的 `hash.Hash` 对象中。
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**练习 12.9**：[hash_md5.go](exercises/chapter_12/hash_md5.go)：
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在示例 12.20 中检验 md5 算法。
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## 链接
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- [目录](directory.md)
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- 上一节：[用 Gob 传输数据](12.11.md)
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- 下一章：[错误处理与测试](13.0.md)
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