crypto: chacha20-generic - add XChaCha20 support

[linux.git] / crypto / Kconfig

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 62dbd1a99fa3b1bcab788c629532a7227987bfe3..75ebd1a2746c4b016544bdf371bb748fbf7a2e80 100644 (file)
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1403,18 +1403,22 @@ config CRYPTO_SALSA20
          Bernstein <djb@cr.yp.to>. See <http://cr.yp.to/snuffle.html>
 
 config CRYPTO_CHACHA20
-       tristate "ChaCha20 cipher algorithm"
+       tristate "ChaCha20 stream cipher algorithms"
        select CRYPTO_BLKCIPHER
        help
-         ChaCha20 cipher algorithm, RFC7539.
+         The ChaCha20 and XChaCha20 stream cipher algorithms.
 
          ChaCha20 is a 256-bit high-speed stream cipher designed by Daniel J.
          Bernstein and further specified in RFC7539 for use in IETF protocols.
-         This is the portable C implementation of ChaCha20.
-
-         See also:
+         This is the portable C implementation of ChaCha20.  See also:
          <http://cr.yp.to/chacha/chacha-20080128.pdf>
 
+         XChaCha20 is the application of the XSalsa20 construction to ChaCha20
+         rather than to Salsa20.  XChaCha20 extends ChaCha20's nonce length
+         from 64 bits (or 96 bits using the RFC7539 convention) to 192 bits,
+         while provably retaining ChaCha20's security.  See also:
+         <https://cr.yp.to/snuffle/xsalsa-20081128.pdf>
+
 config CRYPTO_CHACHA20_X86_64
        tristate "ChaCha20 cipher algorithm (x86_64/SSSE3/AVX2)"
        depends on X86 && 64BIT