Question: I need the source code of the OpenSSL API functions for EVP encryption, like `EVP_aes_256_cbc`. After much searching, all I could find were the headers of the functions in `openssl/evp.h`, but no source code in a `.c` file.

Where can I find the source code?

Answer: 
You'll find the final CBC mode implementation in [`cbc128.c`](http://docs.huihoo.com/doxygen/openssl/1.0.1c/cbc128_8c_source.html) and AES itself in [`AES.c`](http://docs.huihoo.com/doxygen/openssl/1.0.1c/aes__cbc_8c_source.html). Mind that the EVP are high level functions that could use an engine - for instance using a hardware module (HSM) - or AES-NI CPU instructions instead. Searching for a single source file is therefore bunk.
> 
> I need the source code of openssl api functions evp encription... "EVP\_AES\_256\_CBC"...
> 
> 
> 

There is no function `EVP_AES_256_CBC`:

```
$ cd openssl-1.0.1g
$ grep -R EVP_AES_256_CBC *
$ 

```

So searching for it should turn up no results.

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> 
> where can I find the source code 
> 
> 
> 

As user3553031 pointed out, you can get the source code for OpenSSL at [OpenSSL: Source, Tarballs](https://www.openssl.org/source/).

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What do you really want?