Decryption problem using RSA

Question

I have following steps to perform for decryption

base64 decode the response
Decrypt the first 128 bytes with the RSA1024 public key. Key is in base64 encoded X509 format with PKCS1 padding.

My code looks like this:

$decodedString = $this->base64UrlDecode($string); //does proper url decoding                
$publicKey = file_get_contents("public.key",true); 
$pub_key = openssl_get_publickey($publicKey);   
openssl_public_decrypt($decodedString,$decrypted,$pub_key,OPENSSL_PKCS1_PADDING);
var_dump($decrypted);

I am not able to get anything in $decrypted variable. If I try to base64 decode public key before using it, I am getting error of not a valid public key. What I am missing or doing wrong to achieve mentioned 2 steps?

is it something related to creation of that .key file?

Kris
– Kris

2011-09-19 11:38:19 +00:00
Commented Sep 19, 2011 at 11:38 — Kris
– Kris, Commented Sep 19, 2011 at 11:38

robert · Accepted Answer · 2011-09-19 11:40:59Z

1

See this comment for openssl_pkey_get_public:

http://www.php.net/manual/en/function.openssl-pkey-get-public.php#101513

PKCS1 padding poses a problem to that function, it seems.

answered Sep 19, 2011 at 11:40

robert

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1 Comment

CM. Over a year ago

it works only for 2048 bits. I need a solution for 1024 bits :(

CM. · Accepted Answer · 2011-10-07 09:29:56Z

0

It was actually a problem with how I was getting response. By doing urldecode before base64 decoding I am able to get proper results.

$decodedString = $this->base64UrlDecode(urldecode($string));

answered Oct 7, 2011 at 9:29

CM.

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