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Go Requires Chilkat v11.0.0+

Duplicate openssl dgst -md5 -sign myKey.pem something.txt | openssl enc -base64 -A

See more RSA Examples

Demonstrates how to duplicate the creation of an RSA signature produced by this OpenSSL command:
openssl dgst -md5 -sign myKey.pem something.txt | openssl enc -base64 -A

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Go
    success := false

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

    pkey := chilkat.NewPrivateKey()

    //  Load the private key from an RSA PEM file:
    success = pkey.LoadPemFile("myKey.pem")

    rsa := chilkat.NewRsa()

    //  Import the private key into the RSA component:
    success = rsa.UsePrivateKey(pkey)
    if success == false {
        fmt.Println(rsa.LastErrorText())
        pkey.DisposePrivateKey()
        rsa.DisposeRsa()
        return
    }

    //  OpenSSL uses BigEndian byte ordering:
    rsa.SetLittleEndian(false)

    //  The resulting signature will be a Base64 string:
    rsa.SetEncodingMode("base64")

    //  For simplicity, we're not loading
    //  the data to be signed from a file.  We are instead simply
    //  using a literal string value.  
    strData := "This is the text to be signed."

    //  Hash the input using MD5, and then sign the hash:
    //  Other valid hash algorithm choices are "md2" and "sha-1".
    base64Sig := rsa.SignStringENC(strData,"md5")

    fmt.Println(*base64Sig)

    fmt.Println("Success!")

    pkey.DisposePrivateKey()
    rsa.DisposeRsa()