> For the complete documentation index, see [llms.txt](https://www.kryptor.co.uk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.kryptor.co.uk/tutorial/decrypting-received-files.md).

# Decrypting received files

## Using a public key

Kryptor will convert the shared secret for the (recipient private, sender public) key pair into the unique encryption key per file/directory used for encryption.

The sender cannot decrypt the files/directories they sent; only you (the recipient) and any other recipients can.

**You must specify your private key and the sender's public key**. You'll be asked to decrypt your private key using your passphrase. For security reasons, this involves a slight delay.

Here's an example of how to use your default encryption private key:

```bash
$ kryptor -d -y Cu//2M5FqAnxmW7PiKxIqLmKEPNxT1Kdkm4U3K/Gr++6OAQ= file.txt.bin

Enter your private key passphrase:

```

Here's an example using a private key not stored in the [default folder](/tutorial/generating-a-new-key-pair.md):

```bash
$ kryptor -d -x:"C:\Users\samuel-lucas6\Documents\encryption.private" -y Cu//2M5FqAnxmW7PiKxIqLmKEPNxT1Kdkm4U3K/Gr++6OAQ= file.txt.bin

Enter your private key passphrase:

```

## Using a symmetric key

Kryptor will convert the symmetric key into the unique encryption key per file/directory used for encryption. Unlike using a passphrase, this involves no delay.

Here's an example:

```bash
$ kryptor -d -k PSK/I1SkTbgoylRxiW3w0wcYmovWTWgC54bPmpgsiQrgO3c= file.txt.bin
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://www.kryptor.co.uk/tutorial/decrypting-received-files.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.