(Perl) RSA-OAEP with SHA256 hashing

RSA encrypt a SHA256 hash with OAEP padding.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

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

$pubkey = chilkat::CkPublicKey->new();

$sbPem = chilkat::CkStringBuilder->new();
$bCrlf = 1;
$sbPem->AppendLine("-----BEGIN PUBLIC KEY-----",$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 != 1) {
    print $pubkey->lastErrorText() . "\r\n";
    exit;
}

# Build a small string to encrypt
$json = chilkat::CkJsonObject->new();
$json->UpdateString("example","123");
$json->UpdateString("hello","world");
print $json->emit() . "\r\n";

# 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::CkRsa->new();
$rsa->put_OaepPadding(1);
$rsa->put_OaepHash("SHA-256");
$rsa->ImportPublicKeyObj($pubkey);
$rsa->put_EncodingMode("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 = 0;
$encryptedStr = $rsa->encryptStringENC($json->emit(),$bUsePrivateKey);
if ($rsa->get_LastMethodSuccess() != 1) {
    print $rsa->lastErrorText() . "\r\n";
    exit;
}

print "Result: " . $encryptedStr . "\r\n";