Fast and memory-efficient streaming hash functions and base64 encoding / decoding.

Hashes strings and raw vectors directly. Stream hashes files potentially larger than memory, as well as in-memory objects through R’s serialization mechanism.

Implementations include the SHA-256, SHA-3 and ‘Keccak’ cryptographic hash functions, SHAKE256 extendable-output function (XOF), and ‘SipHash’ pseudo-random function.

### Overview

#### SHA-3

For the SHA-3 cryptographic hash algorithm, specify ‘bits’ as `224`

, `256`

, `384`

or `512`

:

```
sha3("secret base")
#> [1] "a721d57570e7ce366adee2fccbe9770723c6e3622549c31c7cab9dbb4a795520"
sha3("secret base", convert = FALSE)
#> [1] a7 21 d5 75 70 e7 ce 36 6a de e2 fc cb e9 77 07 23 c6 e3 62 25 49 c3 1c 7c
#> [26] ab 9d bb 4a 79 55 20
sha3("秘密の基地の中", bits = 512L)
#> [1] "e30cdc73f6575c40d55b5edc8eb4f97940f5ca491640b41612e02a05f3e59dd9c6c33f601d8d7a8e2ca0504b8c22f7bc69fa8f10d7c01aab392781ff4ae1e610"
```

#### Stream hash R objects

All other objects are stream hashed using R serialization

- memory-efficient as performed without allocation of the serialized object
- portable as always uses R serialization version 3, big-endian representation, skipping headers (which contain R version and native encoding information)

```
sha3(data.frame(a = 1, b = 2), bits = 224L)
#> [1] "03778aad53bff7dd68caab94374bba6f07cea235fb97b3c52cf612e9"
sha3(NULL)
#> [1] "b3e37e4c5def1bfb2841b79ef8503b83d1fed46836b5b913d7c16de92966dcee"
```

#### Hash to integer / SHAKE256 XOF

May be used as deterministic random seeds for R’s pseudo random number generators (RNGs).

Specify ‘convert’ as `NA`

(and ‘bits’ as `32`

for a single integer value):

```
shake256("秘密の基地の中", bits = 32L, convert = NA)
#> [1] 2000208511
```

For use in parallel computing, this is a valid method for reducing to a negligible probability that RNGs in each process may overlap. This may be especially suitable when first-best alternatives such as using recursive streams are too expensive or unable to preserve reproducibility. ^{[1]}

#### Keccak

```
keccak("secret base", bits = 384L)
#> [1] "c82bae24175676028e44aa08b9e2424311847adb0b071c68c7ea47edf049b0e935ddd2fc7c499333bccc08c7eb7b1203"
```

#### SHA-256

```
sha256("secret base")
#> [1] "1951c1ca3d50e95e6ede2b1c26fefd0f0e8eba1e51a837f8ccefb583a2b686fe"
```

For SHA-256 HMAC, pass a character string or raw vector to ‘key’:

```
sha256("secret base", key = "秘密の基地の中")
#> [1] "ec58099ab21325e792bef8f1aafc0a70e1a7227463cfc410931112705d753392"
```

#### SipHash

SipHash-1-3 is optimized for performance.

Pass a character string or raw vector of up to 16 bytes (128 bits) to ‘key’:

#### Base64 Encoding / Decoding

Strings:

```
base64enc("secret base")
#> [1] "c2VjcmV0IGJhc2U="
base64dec(base64enc("secret base"))
#> [1] "secret base"
```

Raw vectors:

```
base64enc(as.raw(c(1L, 2L, 4L)), convert = FALSE)
#> [1] 41 51 49 45
base64dec(base64enc(as.raw(c(1L, 2L, 4L))), convert = FALSE)
#> [1] 01 02 04
```

Serialized objects:

```
base64enc(data.frame())
#> [1] "WAoAAAADAAQEAQADBQAAAAAFVVRGLTgAAAMTAAAAAAAABAIAAAABAAQACQAAAAVuYW1lcwAAABAAAAAAAAAEAgAAAAEABAAJAAAACXJvdy5uYW1lcwAAAA0AAAAAAAAEAgAAAAEABAAJAAAABWNsYXNzAAAAEAAAAAEABAAJAAAACmRhdGEuZnJhbWUAAAD+"
base64dec(base64enc(data.frame()), convert = NA)
#> data frame with 0 columns and 0 rows
```

### Installation

Install the latest release from CRAN or R-multiverse:

`install.packages("secretbase")`

The current development version is available from R-universe:

`install.packages("secretbase", repos = "https://shikokuchuo.r-universe.dev")`

### Implementation

The SHA-3 Secure Hash Standard was published by the National Institute of Standards and Technology (NIST) in 2015 at doi:10.6028/NIST.FIPS.202. SHA-3 is based on the Keccak algorithm, designed by G. Bertoni, J. Daemen, M. Peeters and G. Van Assche.

The SHA-256 Secure Hash Standard was published by NIST in 2002 at https://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf.

The SHA-256, SHA-3, Keccak, and base64 implementations are based on those by the ‘Mbed TLS’ Trusted Firmware Project at https://www.trustedfirmware.org/projects/mbed-tls.

The SipHash family of pseudo-random functions by Jean-Philippe Aumasson and Daniel J. Bernstein was published in 2012 at https://ia.cr/2012/351. ^{[2]}

The SipHash implementation is based on that of Daniele Nicolodi, David Rheinsberg and Tom Gundersen at https://github.com/c-util/c-siphash, which is in turn based on the reference implementation by Jean-Philippe Aumasson and Daniel J. Bernstein released to the public domain at https://github.com/veorq/SipHash.

### References

[1] Pierre L’Ecuyer, David Munger, Boris Oreshkin and Richard Simard (2017), *“Random numbers for parallel computers: Requirements and methods, with emphasis on GPUs”*, Mathematics and Computers in Simulation, Vol. 135, May 2017, pp. 3-17 doi:10.1016/j.matcom.2016.05.00.

[2] Jean-Philippe Aumasson and Daniel J. Bernstein (2012), *“SipHash: a fast short-input PRF”*, Paper 2012/351, Cryptology ePrint Archive, https://ia.cr/2012/351.

### Links

◈ secretbase R package: https://shikokuchuo.net/secretbase/

Mbed TLS website: https://www.trustedfirmware.org/projects/mbed-tls

SipHash streaming implementation: https://github.com/c-util/c-siphash

SipHash reference implementation: https://github.com/veorq/SipHash

–

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