R: Create AES block cipher object

AES {digest} | R Documentation

## Create AES block cipher object

### Description

This creates an object that can perform the Advanced Encryption Standard (AES) block cipher.

### Usage

    AES(key, mode=c("ECB", "CBC", "CTR"), IV=NULL)

### Arguments

`key` | The key as a 16, 24 or 32 byte raw vector for AES-128, AES-192 or AES-256 respectively.
`mode` | The encryption mode to use. Currently only “electronic codebook” (ECB), “cipher-block chaining” (CBC) and “counter” (CTR) modes are supported.
`IV` | The initial vector for CBC mode or initial counter for CTR mode.

### Details

The standard NIST definition of CTR mode doesn't define how the counter is updated, it just requires that it be updated with each block and not repeat itself for a long time. This implementation treats it as a 128 bit integer and adds 1 with each successive block.

### Value

An object of class `"AES"`. This is a list containing the following component functions:

`encrypt(text)` | A function to encrypt a text vector. The text may be a single element character vector or a raw vector. It returns the ciphertext as a raw vector.
`decrypt(ciphertext, raw = FALSE)` | A function to decrypt the ciphertext. In ECB mode, the same AES object can be used for both encryption and decryption, but in CBC and CTR modes a new object needs to be created, using the same initial `key` and `IV` values.
`IV()` | Report on the current state of the initialization vector. As blocks are encrypted or decrypted in CBC or CTR mode, the initialization vector is updated, so both operations can be performed sequentially on subsets of the text or ciphertext.
`block_size(), key_size(), mode()` | Report on these aspects of the AES object.

### Author(s)

The R interface was written by Duncan Murdoch. The design is loosely based on the Python Crypto implementation. The underlying AES implementation is by Christophe Devine.

### References

United States National Institute of Standards and Technology (2001). "Announcing the ADVANCED ENCRYPTION STANDARD (AES)". Federal Information Processing Standards Publication 197. https://csrc.nist.gov/publications/fips/fips197/fips-197.pdf.

Morris Dworkin (2001). "Recommendation for Block Cipher Modes of Operation". NIST Special Publication 800-38A 2001 Edition. https://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf.

### Examples

    # First in ECB mode: the repeated block is coded the same way each time
    msg <- as.raw(c(1:16, 1:16))
    key <- as.raw(1:16)
    aes <- AES(key, mode="ECB")
    aes$encrypt(msg)
    aes$decrypt(aes$encrypt(msg), raw=TRUE)

    # Now in CBC mode:  each encoding is different
    iv <- sample(0:255, 16, replace=TRUE)
    aes <- AES(key, mode="CBC", iv)
    code <- aes$encrypt(msg)
    code

    # Need a new object for decryption in CBC mode
    aes <- AES(key, mode="CBC", iv)
    aes$decrypt(code, raw=TRUE)

    # FIPS-197 examples

    hextextToRaw <- function(text) {
      vals <- matrix(as.integer(as.hexmode(strsplit(text, "")[[1]])), ncol=2, byrow=TRUE)
      vals <- vals %*% c(16, 1)
      as.raw(vals)
    }

    plaintext       <- hextextToRaw("00112233445566778899aabbccddeeff")

    aes128key       <- hextextToRaw("000102030405060708090a0b0c0d0e0f")
    aes128output    <- hextextToRaw("69c4e0d86a7b0430d8cdb78070b4c55a")
    aes <- AES(aes128key)
    aes128 <- aes$encrypt(plaintext)
    stopifnot(identical(aes128, aes128output))
    stopifnot(identical(plaintext, aes$decrypt(aes128, raw=TRUE)))

    aes192key       <- hextextToRaw("000102030405060708090a0b0c0d0e0f1011121314151617")
    aes192output    <- hextextToRaw("dda97ca4864cdfe06eaf70a0ec0d7191")
    aes <- AES(aes192key)
    aes192 <- aes$encrypt(plaintext)
    stopifnot(identical(aes192, aes192output))
    stopifnot(identical(plaintext, aes$decrypt(aes192, raw=TRUE)))

    aes256key       <- hextextToRaw("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
    aes256output     <- hextextToRaw("8ea2b7ca516745bfeafc49904b496089")
    aes <- AES(aes256key)
    aes256 <- aes$encrypt(plaintext)
    stopifnot(identical(aes256, aes256output))
    stopifnot(identical(plaintext, aes$decrypt(aes256, raw=TRUE)))

    # SP800-38a examples

    plaintext <- hextextToRaw(paste("6bc1bee22e409f96e93d7e117393172a",
                                    "ae2d8a571e03ac9c9eb76fac45af8e51",
                                    "30c81c46a35ce411e5fbc1191a0a52ef",
                                    "f69f2445df4f9b17ad2b417be66c3710",sep=""))
    key <- hextextToRaw("2b7e151628aed2a6abf7158809cf4f3c")

    ecb128output <- hextextToRaw(paste("3ad77bb40d7a3660a89ecaf32466ef97",
                                       "f5d3d58503b9699de785895a96fdbaaf",
                                       "43b1cd7f598ece23881b00e3ed030688",
                                       "7b0c785e27e8ad3f8223207104725dd4",sep=""))
    aes <- AES(key)
    ecb128 <- aes$encrypt(plaintext)
    stopifnot(identical(ecb128, ecb128output))
    stopifnot(identical(plaintext, aes$decrypt(ecb128, raw=TRUE)))

    cbc128output <- hextextToRaw(paste("7649abac8119b246cee98e9b12e9197d",
                                       "5086cb9b507219ee95db113a917678b2",
                                       "73bed6b8e3c1743b7116e69e22229516",
                                       "3ff1caa1681fac09120eca307586e1a7",sep=""))
    iv <- hextextToRaw("000102030405060708090a0b0c0d0e0f")
    aes <- AES(key, mode="CBC", IV=iv)
    cbc128 <- aes$encrypt(plaintext)
    stopifnot(identical(cbc128, cbc128output))
    aes <- AES(key, mode="CBC", IV=iv)
    stopifnot(identical(plaintext, aes$decrypt(cbc128, raw=TRUE)))

    ctr128output <- hextextToRaw(paste("874d6191b620e3261bef6864990db6ce",
                                       "9806f66b7970fdff8617187bb9fffdff",
                                       "5ae4df3edbd5d35e5b4f09020db03eab",
                                       "1e031dda2fbe03d1792170a0f3009cee",sep=""))
    iv <- hextextToRaw("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff")
    aes <- AES(key, mode="CTR", IV=iv)
    ctr128 <- aes$encrypt(plaintext)
    stopifnot(identical(ctr128, ctr128output))
    aes <- AES(key, mode="CTR", IV=iv)
    stopifnot(identical(plaintext, aes$decrypt(ctr128, raw=TRUE)))

[Package digest version 0.6.15 Index]