“**Error error0308010cdigital envelope routinesunsupported**” is a common error that can occur when attempting to use OpenSSL to encrypt or decrypt data. This error occurs when OpenSSL encounters an unsupported algorithm or encryption method.

OpenSSL is an open-source implementation of the SSL and TLS protocols, which are widely used to secure communication over the internet. It provides a set of libraries and utilities that developers can use to implement secure communication in their applications.

To understand this error in more detail, we first need to understand what digital envelopes are and how they are used in encryption.

## What are Digital Envelopes?

Digital envelopes are a common technique used in public key cryptography to secure data. The process involves encrypting the data using a symmetric encryption algorithm (such as AES or 3DES) and then encrypting the symmetric key using the recipient’s public key.

The recipient can then use their private key to decrypt the symmetric key and then use it to decrypt the data. This process is used to ensure that only the intended recipient can access the data.

## The Error:0308010c

“**Error error0308010cdigital envelope routinesunsupported**” occurs when OpenSSL encounters an unsupported encryption algorithm or method during the digital envelope creation process.

The error message itself is not very informative and does not provide much information on what went wrong. However, there are a few common causes of this error, which we will discuss in the following sections.

### Cause 1: Unsupported Algorithm

One common cause of the error “error:0308010c:digital envelope routines::unsupported” is an unsupported encryption algorithm. OpenSSL supports a wide range of encryption algorithms, including AES, 3DES, RC4, and Blowfish, among others.

If you are trying to use an encryption algorithm that is not supported by OpenSSL, you will encounter this error. To resolve this issue, you can either use a supported encryption algorithm or add support for the unsupported algorithm.

### Cause 2: Unsupported Key Size

Another common cause of the error “error:0308010c:digital envelope routines::unsupported” is an unsupported key size. Encryption algorithms typically have a range of supported key sizes, and if you try to use a key size that is not supported, you will encounter this error.

For example, if you are trying to use AES with a key size of 256 bits, but OpenSSL only supports AES with a key size of up to 128 bits, you will encounter this error. To resolve this issue, you can either use a supported key size or modify OpenSSL to support the key size you need.

### Cause 3: Incorrect Parameters

The error “error:0308010c:digital envelope routines::unsupported” can also occur if you pass incorrect parameters to OpenSSL when creating a digital envelope. This could be due to a typo or an incorrect data type, for example.

To resolve this issue, you need to carefully review the parameters you are passing to OpenSSL and ensure they are correct.

## How to solve Error error0308010cdigital envelope routinesunsupported

Now that we have a better understanding of what causes the error “error:0308010c:digital envelope routines::unsupported,” let’s look at some solutions.

### Solution 1: Use a Supported Algorithm

If you are encountering this error due to an unsupported encryption algorithm, the easiest solution is to use a supported algorithm. OpenSSL supports a wide range of encryption algorithms, so it is likely that there is a supported algorithm that meets your needs.

To use a supported algorithm, you need to modify your code to specify the algorithm you want to use. For example, if you want to use AES, you would use the following code:

```
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv);
```

Solution 2: Modify OpenSSL to Support the Algorithm

If you absolutely need to use an unsupported algorithm, you can modify OpenSSL to add support for the algorithm. This requires modifying the OpenSSL source code and recompiling it.

To modify OpenSSL, you need to locate the implementation of the encryption algorithm you want to use and add it to the code. Once you have added the implementation, you need to recompile OpenSSL and use the modified version in your code.

This solution requires a deep understanding of OpenSSL and can be quite challenging. However, it may be necessary if you have specific requirements that cannot be met with the supported algorithms.

### Solution 3: Pass Correct Parameters

If you are encountering this error due to incorrect parameters, the solution is to carefully review the parameters you are passing to OpenSSL and ensure they are correct. This could involve double-checking the data types or verifying that the values are correct.

To avoid this issue in the future, it is a good idea to validate your inputs and ensure that they are correct before passing them to OpenSSL.

**Example Code**

To demonstrate how to use OpenSSL to encrypt data, here is an example implementation:

```
#include <openssl/evp.h>
int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
unsigned char *iv, unsigned char *ciphertext)
{
EVP_CIPHER_CTX *ctx;
int len;
int ciphertext_len;
/* Create and initialize the context */
if(!(ctx = EVP_CIPHER_CTX_new())) return -1;
if(1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
return -1;
/* Encrypt the data */
if(1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len))
return -1;
ciphertext_len = len;
/* Finalize the encryption */
if(1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) return -1;
ciphertext_len += len;
/* Clean up */
EVP_CIPHER_CTX_free(ctx);
return ciphertext_len;
}
```

This code uses AES-128 CBC mode to encrypt the data. The key and IV are passed in as parameters, and the ciphertext is returned.

## Conclusion

- OpenSSL is an open-source implementation of SSL and TLS protocols for securing communication over the internet
- “Error error0308010cdigital envelope routines unsupported” occurs when OpenSSL encounters an unsupported encryption algorithm or method during the digital envelope creation process
- Digital envelopes involve encrypting data using a symmetric encryption algorithm and then encrypting the symmetric key using the recipient’s public key
- Causes of the error include an unsupported algorithm, unsupported key size, and incorrect parameters
- Solutions to the error include using a supported algorithm, modifying OpenSSL to support the algorithm, and passing correct parameters
- To avoid encountering the error, it is advisable to validate inputs and ensure they are correct before passing them to OpenSSL

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