[Composer] Upgrade to phpseclib version 3

- Create custom Key file format for Salmon Magic key
- Remove obsolete pemToME and MEtoPem Crypto methods
- Remove unused newECKeypair Crypto method
- Switch to constant-time Base64 encode/decode in Base64Url Strings methods

src/Module/OStatus/Salmon.php

@@ -142,14 +142,9 @@ class Salmon extends \Friendica\BaseModule
 			throw new HTTPException\BadRequestException();
 		}
 
-		$key_info = explode('.', $key);
+		$this->logger->info('Key details', ['info' => $key]);
 
-		$m = Strings::base64UrlDecode($key_info[1]);
-		$e = Strings::base64UrlDecode($key_info[2]);
-
-		$this->logger->info('Key details', ['info' => $key_info]);
-
-		$pubkey = Crypto::meToPem($m, $e);
+		$pubkey = SalmonProtocol::magicKeyToPem($key);
 
 		// We should have everything we need now. Let's see if it verifies.
 

src/Module/PublicRSAKey.php

@@ -23,11 +23,9 @@ namespace Friendica\Module;
 
 use Friendica\BaseModule;
 use Friendica\Core\System;
-use Friendica\DI;
 use Friendica\Model\User;
 use Friendica\Network\HTTPException\BadRequestException;
-use Friendica\Util\Crypto;
-use Friendica\Util\Strings;
+use Friendica\Protocol\Salmon;
 
 /**
  * prints the public RSA key of a user
@@ -47,9 +45,10 @@ class PublicRSAKey extends BaseModule
 			throw new BadRequestException();
 		}
 
-		Crypto::pemToMe($user['spubkey'], $modulus, $exponent);
-
-		$content = 'RSA' . '.' . Strings::base64UrlEncode($modulus, true) . '.' . Strings::base64UrlEncode($exponent, true);
-		System::httpExit($content, Response::TYPE_BLANK, 'application/magic-public-key');
+		System::httpExit(
+			Salmon::salmonKey($user['spubkey']),
+			Response::TYPE_BLANK,
+			'application/magic-public-key'
+		);
 	}
 }