PHP OpenSSL Public Key Encryption With String Public Key

Question

I have a public key

stored as a base64 encoded string (in MySQL, set as $row['public_key'])

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

in PHP. I'm trying to use this string to encrypt string data, but it just fails without telling me why when I use the following code:

$success = openssl_public_encrypt($data, $encrypted, base64_decode($row['public_key']));

When the above is run, $success is always false and $encrypted is blank. I've tried running the public key through openssl_pkey_get_public() and sending the resource to openssl_public_encrypt() with no luck either. Writing to a file is not an option, nor is storing the private key.

Does anyone know how to get this to work? (or does it work for everyone else and it's just a weird server issue?)

EDIT: Since there seems to be some confusion about my issue, here is the testing code I'm using and its output. (Note: I've removed the base64 encoding, just to see if that made any difference)

$pubkey = openssl_get_publickey($row['public_key']);
$publicKey = openssl_pkey_get_details($res);
$encrypted = null;
$success = openssl_public_encrypt($data, $encrypted, $pubkey);
print "\npubkey1 " . $row['public_key'];
print "\npubkey2 " . $pubkey;
print "\npubkey3 " . $publicKey;
print "\npubkey4 " . $publicKey["key"];
print "\nencryption " . ($success ? 'true' : 'false') . ' "' . $encrypted . '"';
$success = openssl_public_encrypt($data, $encrypted, $row['public_key']);
print "\nencryption2 " . ($success ? 'true' : 'false') . ' "' . $encrypted . '"';

Output:

pubkey1 -----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA89FgfElm36q7iAf8frqa
o58naoROsAljaFbmztfnqlmzXfyijK5CNJFdkUCgsu2zGxN7UlGiBOassTd4ijWm
1rz6/ad9fGXplfMGxZxyPCz31VreSWXmTG/PeSIYs1Co+dibV3imYt5jTxfLs7BZ
WsT8nuLxGPw/o/gyKut0Ru+jXI2GgT4s3SylXinn/IbIA497SohqYA7/ViQnBwSL
ZKUysOx2QgBmc9m0viRqDSKNUtDw7+L7bjhlwgZUGr6fxfTuNj9PWo97aPSE74CD
owYYl2ToTboKSjZUszeNwQKpUnlHY/DBkwmYUJ7SAYDY70VNooadN5dZ4ehjdaka
6QIDAQAB
-----END PUBLIC KEY-----

pubkey2 Resource id #50
pubkey3 
pubkey4 
encryption false ""
encryption2 false ""

@halfer Your encryption class does essentially what I'm already doing. — geoffreak
– geoffreak, Commented Jun 13, 2013 at 13:59

j. andrew shusta · Accepted Answer · 2013-06-12 22:36:27Z

2

The key that you should pass to this function is a PHP resource object, and not the string representation of the key itself.

$pubkey = openssl_get_publickey(base64_decode($row['public_key']));
$success = openssl_public_encrypt($data, $encrypted, $pubkey);

answered Jun 12, 2013 at 22:36

j. andrew shusta

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1 Comment

geoffreak Over a year ago

Sadly, this doesn't appear to make any difference. See my edits.

Community · Accepted Answer · 2017-05-23 12:00:49Z

1

So the issue actually relates to the data. PKI for php has a really small length restriction and can't be used to encrypt large amounts of data. Instead you're supposed to use PKI to encrypt a symmetric key which is then used to encrypt/decrypt data.

See more @ How to encrypt long strings in PHP?

edited May 23, 2017 at 12:00

CommunityBot

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answered Jun 13, 2013 at 15:42

geoffreak

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1 Comment

neubert Over a year ago

This isn't a "PKI for php" issue. It's an RSA issue. RSA using PKCS1 padding, only lets you do do numbers that are the length of the modulus (in bytes) - 11. I've replied to the other topic as well.

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