CODEWITHSUNDEEP
phpencryptionrsaphpseclib
MPainter
MPainter

Reputation: 79

Trouble with RSA using phpseclib in PHP

I'm trying to use the RSA implementation in phpseclib, I thought it would be easier to do the code once in a function and re-use the function. When I've tried texting the code I get a error saying "decryption error" Testing also made me realise that the ciphertext was different every time the code ran, so I'm clearly doing something wrong there!

The code for the functions is:

require_once "Crypt/RSA.php";
require_once "Crypt/AES.php";

//Function for encrypting with RSA
function rsa_encrypt($string, $public_key)
{
    //Create an instance of the RSA cypher and load the key into it
    $cipher = new Crypt_RSA();
    $cipher->loadKey($public_key);
    //Set the encryption mode
    $cipher->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
    //Return the encrypted version
    return base64_encode($cipher->encrypt($string));
}

//Function for decrypting with RSA 
function rsa_decrypt($string, $private_key)
{
    //Create an instance of the RSA cypher and load the key into it
    $cipher = new Crypt_RSA();
    $cipher->loadKey($private_key);
    //Set the encryption mode
    $cipher->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
    //Return the decrypted version
    return $cipher->decrypt($string);
}

I've tried to test it using the following: (The keys are just for testing so that's why its hardcoded). It is in here that everytime the code is run that the value of $ciphertext changes everytime

//Private key
$private_key = "-----BEGIN RSA PRIVATE KEY----- MIICXAIBAAKBgQCU+1bLfPmcY7qrF/dTbAtuJlv4R/FVc1WEH9HKU0jQjX/n/db9vz/x0i3te/bK LNEcwUhBu+PWPnOt/qVURG9BUT6RsCRFUn0CyGiUKoy45o9K/mJAHmbrNtrUB6ckrYLF75Y50nUN sBVHUDw8yQymmiOBT1gc/KM5s1xTz44LMwIDAQABAoGAGsiMtAyFu23ac0PdvOuhqm3O/vXAF0Ki zxwBVURfxM6LfiOOcRPe5RSKGTW+Cl7AQVEmMlsa/LtBhLhQ9LNQ5L/4oTmRhCGiZZEmccAdjKsx yMeaxkp+ZHvMxMKQNDgYg1CXqrCrpwwUuMUlA26tfxZ3xSFtFyDTaV9mgDQ1IGECQQCkX9Tum7D1 vQTwbhbYnu7eC4eUOaZeGWSEs2csK7U6vfZ3BzUZW/0tPqcSpQqcNxMtY9TiUsNRj1uM6jX3byp7 AkEA6Ab+wvOTNRtES77OAYG9gHGZZ+iXjQJ/6Z7JehN4p41UbDIf9nNUOLUPL9z5V1uOYnl1CWoo Cw95cdhKXxEAqQJBAIU5Or6tp250ZdVslM27ewSyuY9UblfkIsk/EscFIdzbbDAqwkmsefW6yvTc mU3lgYCPYlKRG8c19tCuX1ENY5MCQAz37x9YW975Ai01ofAFn2DheJCNOINCI4IcROiU1AaRaKmP d6fftFJjFFE5iZovXNr2LOt0yn4rxD7vtuBvY9kCQGyty6YCB6qaD7qXPMhLrLbGajAIWd6ETgxv frK/BJu+buPfDky/g1FhI5R9iMtL1xH0JYLJlaVocU+xSeA9DkY= -----END RSA PRIVATE KEY-----";
//Public key
$public_key = "-----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCU+1bLfPmcY7qrF/dTbAtuJlv4R/FVc1WEH9HK U0jQjX/n/db9vz/x0i3te/bKLNEcwUhBu+PWPnOt/qVURG9BUT6RsCRFUn0CyGiUKoy45o9K/mJA HmbrNtrUB6ckrYLF75Y50nUNsBVHUDw8yQymmiOBT1gc/KM5s1xTz44LMwIDAQAB -----END PUBLIC KEY-----";


//Test out the rsa encryption functions
$plaintext = "This is some plaintext to encrypt";
$ciphertext = rsa_encrypt($plaintext, $public_key);
$decipheredtext = rsa_decrypt($ciphertext, $private_key);

//Echo out results
echo sprintf("<h4>Plaintext for RSA encryption:</h4><p>%s</p><h4>After encryption:</h4><p>%s</p><h4>After decryption:</h4><p>%s</p>", $plaintext, $ciphertext, $decipheredtext);

EDIT: Sample output is:

Plaintext for RSA encryption:

This is some plaintext we will encrypt

After encryption:

‘˜!ˆ_枦WýF¦E×9&ùš!´jéÓb÷á劀É7J+۪߯׎È㩨ɣ#(÷)ÃX„)÷O‘­Ë±N@Øv«ÓÌPƒ¹—Âî!a¢¦a&Á½Á˜ö‰ºŠCðJ«vW{uAåoOÂXäÞ#÷ï`agÏ:OŒ

After decryption:

//Nothing is returned, it is blank here

Upvotes: 2

Views: 10762

Answers (1)

user216741
user216741

Reputation:

I think GigaWatt's answer is the correct one. As for this:

Testing also made me realise that the ciphertext was different every time the code ran, so I'm clearly doing something wrong there!

PKCS#1 padding adds random bytes so the ciphertext's will always be different. The PKCS#1 algorithm however knows when the plaintext ends and the random bytes begin so it's able to separate the two and return you the result you're wanting.

EDIT: I got it to work after I replaced the spaces in your keys with new lines. eg.

$private_key = "-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----";
//Public key
$public_key = "-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCU+1bLfPmcY7qrF/dTbAtuJlv4R/FVc1WEH9HK
U0jQjX/n/db9vz/x0i3te/bKLNEcwUhBu+PWPnOt/qVURG9BUT6RsCRFUn0CyGiUKoy45o9K/mJA
HmbrNtrUB6ckrYLF75Y50nUNsBVHUDw8yQymmiOBT1gc/KM5s1xTz44LMwIDAQAB
-----END PUBLIC KEY-----";

Upvotes: 3

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