(Go) RSA-OAEP with SHA256 hashing

RSA encrypt a SHA256 hash with OAEP padding.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    pubkey := chilkat.NewPublicKey()

    sbPem := chilkat.NewStringBuilder()
    bCrlf := true
    sbPem.AppendLine("-----BEGIN PUBLIC KEY-----",bCrlf)
    sbPem.AppendLine("MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF",bCrlf)
    sbPem.AppendLine("3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA",bCrlf)
    sbPem.AppendLine("04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s",bCrlf)
    sbPem.AppendLine("Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF",bCrlf)
    sbPem.AppendLine("wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE",bCrlf)
    sbPem.AppendLine("f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W",bCrlf)
    sbPem.AppendLine("SwIDAQAB",bCrlf)
    sbPem.AppendLine("-----END PUBLIC KEY-----",bCrlf)

    // Load the public key object from the PEM. 
    success := pubkey.LoadFromString(*sbPem.GetAsString())
    if success != true {
        fmt.Println(pubkey.LastErrorText())
        pubkey.DisposePublicKey()
        sbPem.DisposeStringBuilder()
        return
    }

    // Build a small string to encrypt
    json := chilkat.NewJsonObject()
    json.UpdateString("example","123")
    json.UpdateString("hello","world")
    fmt.Println(*json.Emit())

    // This is the JSON to be RSA encrypted:  {"example":"123","hello":"world"}

    // IMPORTANT: RSA encryption is only used to encrypt small amounts of data.
    // RSA is only able to encrypt data to a maximum amount of your key size (2048 bits = 256 bytes) 
    // minus padding / header data (11 bytes for PKCS#1 v1.5 padding, 42 bytes for OAEP).
    // As a result it is often not possible to encrypt files with RSA directly. 
    // RSA is also not meant for this purpose. 
    // 
    // If you want to encrypt more data, you can use something like:
    // 1) Generate a 256-bit random keystring K
    // 2) Encrypt your data with AES-CBC with K
    // 3) Encrypt K with RSA
    // 4) Send both to the other side 

    rsa := chilkat.NewRsa()
    rsa.SetOaepPadding(true)
    rsa.SetOaepHash("SHA-256")
    rsa.ImportPublicKeyObj(pubkey)
    rsa.SetEncodingMode("base64")

    // Note: The OAEP padding uses random bytes in the padding, and therefore each time encryption happens,
    // even using the same data and key, the result will be different --  but still valid.  One should not expect
    // to get the same output.
    bUsePrivateKey := false
    encryptedStr := rsa.EncryptStringENC(*json.Emit(),bUsePrivateKey)
    if rsa.LastMethodSuccess() != true {
        fmt.Println(rsa.LastErrorText())
        pubkey.DisposePublicKey()
        sbPem.DisposeStringBuilder()
        json.DisposeJsonObject()
        rsa.DisposeRsa()
        return
    }

    fmt.Println("Result: ", *encryptedStr)

    pubkey.DisposePublicKey()
    sbPem.DisposeStringBuilder()
    json.DisposeJsonObject()
    rsa.DisposeRsa()