RSAKey 结构体用来存储已经生成的私钥和公钥

通过密钥字符串生成 SecKey，加签，验签

import Foundation
/// 密钥类型
enum KeyType {
    case publicKey
    case privateKey
struct RSASigner {
    /// 通过密钥字符串获取 SecKey 类型的密钥
    /// - Parameter keyString: 密钥字符串
    /// - Parameter keyType: 密钥类型
    static func getSecKey(with keyString: String,keyType: KeyType) -> SecKey? {
        let strippedKey = String(keyString.filter { !" \n\t\r".contains($0) })
        let pemComponents = strippedKey.components(separatedBy: "-----")
        guard pemComponents.count >= 5 else { return nil }
        guard let keyData = Data(base64Encoded: pemComponents[2]) else { return nil }
        let keyClass = keyType == .publicKey ? kSecAttrKeyClassPublic : kSecAttrKeyClassPrivate
        let sizeInBits = keyData.count * MemoryLayout<UInt8>.size
        let keyDict: [CFString: Any] = [
            kSecAttrKeyType: kSecAttrKeyTypeRSA,
            kSecAttrKeyClass: keyClass,
            kSecAttrKeySizeInBits: NSNumber(value: sizeInBits)
        guard let key = SecKeyCreateWithData(keyData as CFData, keyDict as CFDictionary, nil) else { return nil }
        return key
    /// 使用 RSA 算法签名
    /// - Parameter text: 明文
    /// - Parameter privateKey: 密钥
    static func sign(text: String, with privateKey: SecKey) -> String? {
        guard let data = text.data(using: .utf8) else { return nil }
        guard let signedData = SecKeyCreateSignature(privateKey, .rsaSignatureMessagePKCS1v15SHA256, data as CFData , nil) as Data? else { return nil }
        return signedData.base64EncodedString()
    /// 验证签名
    /// - Parameter signature: 签名字符串
    /// - Parameter text: 明文
    /// - Parameter publicKey: 公钥
    static func verify(signature: String, text: String, with publicKey: SecKey) -> Bool {
        guard let signedData = text.data(using: .utf8) else { return false }
        guard let signature = Data(base64Encoded: signature) else {  return false }
        return SecKeyVerifySignature(publicKey, .rsaSignatureMessagePKCS1v15SHA256, signedData  as CFData, signature as CFData,nil)
上面的代码可以通过 RSA 私钥字符串或公钥字符串（如上面所示）生成 Swift 中需要的 SecKey 类型的密钥。使用 SecKey 类型的私钥字符串用来加签，使用 SecKey 类型的公钥用来验签。
定义了一个枚举类型 KeyType 用来标识要生成的是私钥（publicKey）还是公钥（privateKey）
使用 getSecKey(with,keyType)方法来获取 SecKey 类型的密钥
使用 sign(text: with:) 方法类生成签名
使用 verify(signature: text: with) 来验证签名是否正确
func testSignAndVerify() {
    let text = "我是明文"
    guard let privateKey =  RSASigner.getSecKey(with: RSAKey.privateKey, keyType: .privateKey) else {
        return
    guard let signature = RSASigner.sign(text: text, with: privateKey) else {
        return
    guard let pubKey = RSASigner.getSecKey(with: RSAKey.publicKey, keyType: .publicKey) else {
        return
    let result = RSASigner.verify(signature: signature, text: text, with: pubKey)
    print("明文：\(text)")
    print("签名：\(signature)")
    print("验签\(result ? "成功" : "失败")")
明文：我是明文
签名：tD2TjObA/NBRfHjbd3wT4KyAuo+yMWiIXJHVA3qOYMP4ow/WJKzrtaSVQT/COt3ZNMhYY1MTn5syemJ3tcAcFvJtIyprN+rnJMLR9Yu8rrh5yfOa/t55pMsedobUt3ER7SCI5oosyVtvO0EojDK5SG1OFuT9GgfbnSNoFkf2blK7bnuEiLvnlSw/TukKusqeX2OiatvL1qtE3Z0b9RKZRaFl99o/pVo+D5vNGG+K5A9dt6vG/gI0OZYR9YZHT1GIOAryFBejRDeuqP3vniQL0AJRjYXr+cZ4LkiFV1w8X61+Qz6udD6pjeYou3kBwKJOF08mcu+ot9DIh508dQfUtw==
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 iOS
 
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    __Simon__