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--- tanszek:oktatas:techcomm:digital_signature [2024/10/07 15:14] – created knehez
+++ tanszek:oktatas:techcomm:digital_signature [2024/10/07 15:19] (current) – [Simple Digital Signature Using Direct RSA Application] knehez
@@ Line 5: / Line 5: @@
 Public key systems are also known as **asymmetric systems** because different keys are required for encryption and decryption. In **symmetric systems**, the same key is used for both encryption and decryption.
-In asymmetric systems, anyone can send Anna a secret message. But how can we verify the identity of the sender? **Digital signature algorithms** are specialized asymmetric systems. There is a private key used for signing and a public key used to verify the authenticity of the signature.
+In asymmetric systems, anyone can send Alice a secret message. But how can we verify the identity of the sender? **Digital signature algorithms** are specialized asymmetric systems. There is a private key used for signing and a public key used to verify the authenticity of the signature.
 ==== Requirements for a Digital Signature: ====
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 . **Non-repudiation**: The signer cannot later deny having signed the document.
-These requirements make digital signatures a much more secure solution compared to manual (analog) signatures.
+These requirements make digital signatures a much more secure than manual (analog) signatures.
+==== Simple Digital Signature Using Direct RSA Application ====
+In its simplest form, the **RSA algorithm** can also be used for digital signatures.
+The steps are as follows:
+  - Sign the document using your private key
+    - In RSA, the roles of the private and public keys can be reversed: you can encrypt with either key, and the other key (and only that key) can decrypt the message.
+  - If someone encrypts a message with their **private key**, it can be decrypted using their **public key**, thereby verifying the authenticity.
+  - The entire document is encoded as part of the signature (the encoded document itself is the signature).
+  - The signer cannot deny having signed the document because they are the only ones who know the private key necessary to create the signature.
+  - When using the RSA signing method, the document remains unreadable until the signature is verified.
+However, this method can be **inconvenient** in certain cases:
+  * If the recipient does not have access to the **public key**.
+  * If there is not enough computational power available to decrypt the message.
+This explanation outlines how RSA can be applied to digital signatures in a simple manner and highlights the potential limitations of this approach.