Cipher vs signature algorithm?

Question

Hello,
What is the difference between a chipher and a signature algorithm? How can SunJSSE provider have an implementation of SHA1withRSA signature algorithm but not have an implementation of RSA cipher? Don't you need to have the cipher to do the signature?
Thanks for any insights.

Answer 1

Hi!
I'd like to get the same result when I use the Cipher class or when I use the Signature class.
If I use the code below I get different results. Am I doing something wrong? How can I get the same result using these two classes?
Thank you.
//Encryption by the Cipher Class
byte input[]="hello".getBytes();
MessageDigest md = MessageDigest.getInstance("SHA1");
md.update(input);
byte digest[] = md.digest();
Cipher rsaCipher = Cipher.getInstance("RSA");
rsaCipher.init(Cipher.ENCRYPT_MODE, privateKey);
byte[] encryptedData = rsaCipher.doFinal(digest);
System.out.println("textEncrypted="+Base64Utils.base64Encode(encryptedData));
//Encryption by the Signature Class
Signature signatureAlgorithm = Signature.getInstance("SHA1withRSA");
signatureAlgorithm.initSign(privateKey);
signatureAlgorithm.update(input);
encryptedData = signatureAlgorithm.sign();
System.out.println("textEncrypted2="+Base64Utils.base64Encode(encryptedData));