AES_ENCRYPT(3)

💖 AES_ENCRYPT(3) 💖

or: the low-level interface to the AES symmetric cipher, explained by your favorite unix girlie

okay bestie, so this one is from section 3 of the library functions manual and it's literally all about AES_set_encrypt_key, AES_set_decrypt_key, AES_encrypt, AES_decrypt, and AES_cbc_encrypt 🎀 — yes, all five, we're doing the whole squad.

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✨ NAME ✨

AES_set_encrypt_key, AES_set_decrypt_key, AES_encrypt, AES_decrypt, AES_cbc_encrypt — the low-level interface to the AES symmetric cipher. that's the vibe 💅

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🌸 SYNOPSIS 🌸

#include <openssl/aes.h>

int
AES_set_encrypt_key(const unsigned char *userKey, const int bits,
    AES_KEY *key);

int
AES_set_decrypt_key(const unsigned char *userKey, const int bits,
    AES_KEY *key);

void
AES_encrypt(const unsigned char *in, unsigned char *out,
    const AES_KEY *key);

void
AES_decrypt(const unsigned char *in, unsigned char *out,
    const AES_KEY *key);

void
AES_cbc_encrypt(const unsigned char *in, unsigned char *out,
    size_t length, const AES_KEY *key, unsigned char *ivec,
    const int enc);

like, copy that verbatim into your editor, do not retype it from memory, i'm begging 😭

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🦋 DESCRIPTION 🦋

so these functions provide a low-level interface to the AES symmetric cipher algorithm — it's also called Rijndael, which is honestly such a main character name 🌈. but here's the tea: for reasons of flexibility, it is recommended that application programs use the high-level interface described in EVP_EncryptInit(3) and EVP_aes_128_cbc(3) instead whenever possible. like, the low-level one is right there, but the high-level one ate 🫶

AES_KEY is a structure that can hold up to 60 int values and a number of rounds. that's it, that's the struct lore 💜

AES_set_encrypt_key() expands the userKey, which is bits long, into the key structure to prepare for encryption. and the way the numbers line up?? obsessed. here's the full breakdown — the number of bits and bytes read from userKey, the number of int values stored into key, and the number of rounds:

• bits 128 — bytes 16, ints 44, rounds 10
• bits 192 — bytes 24, ints 52, rounds 12
• bits 256 — bytes 32, ints 60, rounds 14

AES_set_decrypt_key() does the same, but in preparation for decryption. literally the same ritual, different direction ✨

AES_encrypt() reads a single 16 byte block from *in, encrypts it with the key, and writes the 16 resulting bytes to *out. and the cute part?? the 16 byte buffers starting at in and out can overlap, and in and out can even point to the same memory location 👑 iconic behavior, no notes.

AES_decrypt() decrypts a single block and is otherwise identical to AES_encrypt(). same girl, opposite direction 💅

If enc is non-zero, AES_cbc_encrypt() encrypts len bytes at in to out using the 128 bit key and the 128 bit initialization vector ivec in CBC mode. If enc is 0, AES_cbc_encrypt() performs the corresponding decryption. so like... enc is the switch, bestie, don't fumble it 🙈

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🎀 RETURN VALUES 🎀

AES_set_encrypt_key() and AES_set_decrypt_key() return 0 for success, -1 if userKey or key is NULL, or -2 if the number of bits is unsupported.

so: 0 = slay, -1 = you passed a NULL 😭, -2 = that bit count is not invited to the party 💀. that's the whole return value situation.

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🔥 SEE ALSO 🔥

• crypto(3)
• EVP_aes_128_cbc(3)
• EVP_EncryptInit(3)

go read those next, i'm serious, the high-level ones are the moment 🫶

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⭐ STANDARDS ⭐

ISO/IEC 18033-3:2010 Information technology — Security techniques — Encryption algorithms — Part 3: Block ciphers

yes the whole title, em dashes and all, i'm not paraphrasing a standard 💖

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👑 HISTORY 👑

These functions first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2. veterans fr fr 🌸

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🧚 AUTHORS 🧚

• Vincent Rijmen
• Antoon Bosselaers
• Paulo Barreto

the literal legends, we stan 💜

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ok one last vibe check before you go: this is the low-level interface. if you can use EVP_EncryptInit(3) and EVP_aes_128_cbc(3), please do — the manpage itself says so, i'm just the messenger 🦋

mwah, go encrypt something responsibly 💅✨

this page came from the Debian crew, dated August 28, 2019 — aes_encrypt(3), still serving looks 💖