golang 通过已知的priKey 对字符串做 RSA加密

要使用已知的私钥对字符串进行RSA加密，需要进行以下步骤：

将私钥加载到RSA密钥对结构中。私钥可以是PEM格式或DER格式。如果是PEM格式，可以使用ParsePKCS1PrivateKey或ParsePKCS8PrivateKey函数来加载私钥。如果是DER格式，可以使用x509.ParsePKCS1PrivateKey或x509.ParsePKCS8PrivateKey函数来加载私钥。

// 示例代码加载PEM格式的私钥
import (
    "crypto/rsa"
    "crypto/x509"
    "encoding/pem"
    "io/ioutil"
)

func loadPrivateKeyFromPEM(pemFilePath string) (*rsa.PrivateKey, error) {
    pemData, err := ioutil.ReadFile(pemFilePath)
    if err != nil {
        return nil, err
    }

    block, _ := pem.Decode(pemData)
    privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
    if err != nil {
        return nil, err
    }

    return privateKey, nil
}

使用加载的私钥创建RSA加密器。

func createRSACipher(privateKey *rsa.PrivateKey) (*rsa.Encrypter, error) {
    publicKey := &privateKey.PublicKey
    cipher, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, publicKey, []byte{})
    if err != nil {
        return nil, err
    }

    return cipher, nil
}

使用RSA加密器对字符串进行加密。

func encryptString(cipher *rsa.Encrypter, plaintext string) ([]byte, error) {
    ciphertext, err := cipher.Encrypt([]byte(plaintext), nil)
    if err != nil {
        return nil, err
    }

    return ciphertext, nil
}

完整的示例代码如下：

import (
    "crypto/rand"
    "crypto/rsa"
    "crypto/sha256"
    "crypto/x509"
    "encoding/pem"
    "fmt"
    "io/ioutil"
)

func loadPrivateKeyFromPEM(pemFilePath string) (*rsa.PrivateKey, error) {
    pemData, err := ioutil.ReadFile(pemFilePath)
    if err != nil {
        return nil, err
    }

    block, _ := pem.Decode(pemData)
    privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
    if err != nil {
        return nil, err
    }

    return privateKey, nil
}

func createRSACipher(privateKey *rsa.PrivateKey) (*rsa.Encrypter, error) {
    publicKey := &privateKey.PublicKey
    cipher, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, publicKey, []byte{})
    if err != nil {
        return nil, err
    }

    return cipher, nil
}

func encryptString(cipher *rsa.Encrypter, plaintext string) ([]byte, error) {
    ciphertext, err := cipher.Encrypt([]byte(plaintext), nil)
    if err != nil {
        return nil, err
    }

    return ciphertext, nil
}

func main() {
    privateKey, err := loadPrivateKeyFromPEM("private_key.pem")
    if err != nil {
        fmt.Printf("Failed to load private key: %v\n", err)
        return
    }

    cipher, err := createRSACipher(privateKey)
    if err != nil {
        fmt.Printf("Failed to create RSA cipher: %v\n", err)
        return
    }

    plaintext := "Hello, RSA encryption!"
    ciphertext, err := encryptString(cipher, plaintext)
    if err != nil {
        fmt.Printf("Failed to encrypt string: %v\n", err)
        return
    }

    fmt.Printf("Ciphertext: %x\n", ciphertext)
}

请注意，上述代码仅为示例，实际使用时需要根据私钥的格式和加密算法进行相应的调整