• 2015-02-03

    iOS Objective-C RSA encrypt with only public key and descrypt with PHP

    Views: 19938 | 11 Comments

    If you found this post via Google, I am sure this is the final link you click. Your problem will be solved with a single function without any dependency!

    You may have read these posts:

    The first post helps, but it is too old, and it doesn’t provide the full code, the author is so mean!

    The second is nonsense, because you people finding this post must have the exact need as me: iOS RSA encrypt with ONLY the public key. NO .der file, NO CA, NO bullshit!

    OK, lets go on.

    You generate RSA public key and private key with PHP

    $config = array(
    		"digest_alg" => "sha512",
    		"private_key_bits" => 1024,
    		"private_key_type" => OPENSSL_KEYTYPE_RSA,
    		);
    $res = openssl_pkey_new($config);
    openssl_pkey_export($res, $privKey);
    $pubKey = openssl_pkey_get_details($res);
    $pubKey = $pubKey["key"];
    var_dump($privKey, $pubKey); // now you get keys in plain text
    

    It is like:

    -----BEGIN PRIVATE KEY-----
    MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAMQKGp7zSUktNOQk
    PdfcvJ3sWP7O46ENmSO4s0+iDdhHbR7klyt2oj0gXM1sAJj8ZBWFudu8GpiDKqXw
    N88IZemfT5c1LEQshTD1WHfZC6EY2vf9MGl5yGtV5WkU8vDJpg0STUJrCAcJ5Cp/
    m5qqJqgEM5Op6jHzwtzWV3syx+CBAgMBAAECgYEApSzqPzE3d3uqi+tpXB71oY5J
    cfB55PIjLPDrzFX7mlacP6JVKN7dVemVp9OvMTe/UE8LSXRVaFlkLsqXC07FJjhu
    wFXHPdnUf5sanLLdnzt3Mc8vMgUamGJl+er0wdzxM1kPTh0Tmq+DSlu5TlopAHd5
    IqF3DYiORIen3xIwp0ECQQDj6GFaXWzWAu5oUq6j1msTRV3mRZnx8Amxt1ssYM0+
    JLf6QYmpkGFqiQOhHkMgVUwRFqJC8A9EVR1eqabcBXbpAkEA3DQfLVr94vsIWL6+
    VrFcPJW9Xk28CNY6Xnvkin815o2Q0JUHIIIod1eVKCiYDUzZAYAsW0gefJ49sJ4Y
    iRJN2QJAKuxeQX2s/NWKfz1rRNIiUnvTBoZ/SvCxcrYcxsvoe9bAi7KCMdxObJkn
    hNXFQLav39wKbV73ESCSqnx7P58L2QJABmhR2+0A5EDvvj1WpokkqPKmfv7+ELfD
    HQq33LvU4q+N3jPn8C85ZDedNHzx57kru1pyb/mKQZANNX10M1DgCQJBAMKn0lEx
    QH2GrkjeWgGVpPZkp0YC+ztNjaUMJmY5g0INUlDgqTWFNftxe8ROvt7JtUvlgtKC
    XdXQrKaEnpebeUQ=
    -----END PRIVATE KEY-----
    
    -----BEGIN PUBLIC KEY-----
    MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDEChqe80lJLTTkJD3X3Lyd7Fj+
    zuOhDZkjuLNPog3YR20e5JcrdqI9IFzNbACY/GQVhbnbvBqYgyql8DfPCGXpn0+X
    NSxELIUw9Vh32QuhGNr3/TBpechrVeVpFPLwyaYNEk1CawgHCeQqf5uaqiaoBDOT
    qeox88Lc1ld7MsfggQIDAQAB
    -----END PUBLIC KEY-----
    

    Then you send the public key to iOS app

    So, your Objective-C gets only this data(no other bullshit!):

    -----BEGIN PUBLIC KEY-----
    MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDEChqe80lJLTTkJD3X3Lyd7Fj+
    zuOhDZkjuLNPog3YR20e5JcrdqI9IFzNbACY/GQVhbnbvBqYgyql8DfPCGXpn0+X
    NSxELIUw9Vh32QuhGNr3/TBpechrVeVpFPLwyaYNEk1CawgHCeQqf5uaqiaoBDOT
    qeox88Lc1ld7MsfggQIDAQAB
    -----END PUBLIC KEY-----
    

    You need a function to do RSA encryption

    + (NSString *)encryptString:(NSString *)str publicKey:(NSString *)pubKey;
    

    YES! No SecRef, No Security.h, with exactly one function, of two arguments.

    Now your code is as clean as

    NSString *pubkey = get_public_key_string_with_http();
    NSString *ret = [RSA encryptString:@"hello world!" publicKey:pubkey];
    NSLog(@"encrypted: %@", ret);
    

    Screw 100% percent security!

    Many Apps don’t need 100% percent security, it only needs encryption, with RSA public key only!

    Objective-C RSA encrypt with public key, full code on GitHub: https://github.com/ideawu/Objective-C-RSA

    Posted by ideawu at 2015-02-03 12:49:01 Tags: ,
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