diff --git a/DESCRIPTION b/DESCRIPTION
index 9446a97..900b74e 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: secretbase
 Type: Package
 Title: Cryptographic Hash and Extendable-Output Functions
-Version: 0.3.0.9007
+Version: 0.3.0.9008
 Description: Fast and memory-efficient streaming hash functions. Performs direct
     hashing of strings, raw bytes, and files potentially larger than memory, as
     well as hashing in-memory objects through R's serialization mechanism,
diff --git a/NAMESPACE b/NAMESPACE
index 586a474..0be9c2c 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -3,5 +3,4 @@
 export(sha256)
 export(sha3)
 export(siphash13)
-export(siphash24)
 useDynLib(secretbase, .registration = TRUE)
diff --git a/NEWS.md b/NEWS.md
index 3d61ab0..36ea353 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,4 +1,4 @@
-# secretbase 0.3.0.9007 (development)
+# secretbase 0.3.0.9008 (development)
 
 * Adds HMAC generation to `sha256()`.
 * Adds SipHash pseudo-random function (PRF) as a fast, cryptographically-strong keyed hash.
diff --git a/R/base.R b/R/base.R
index 931409a..0e5750a 100644
--- a/R/base.R
+++ b/R/base.R
@@ -147,9 +147,8 @@ sha256 <- function(x, key = NULL, convert = TRUE, file)
 #' SipHash Pseudorandom Function
 #'
 #' Returns a fast, cryptographically-strong SipHash keyed hash of the supplied
-#'     object or file. SipHash-1-3 is optimised for performance, whereas
-#'     SipHash-2-4 is recommended for security. Note: SipHash is not a
-#'     cryptographic hash algorithm.
+#'     object or file. SipHash-1-3 is optimised for performance. Note: SipHash
+#'     is not a cryptographic hash algorithm.
 #'
 #' @inheritParams sha3
 #' @param key [default NULL] a character string or raw vector comprising the 16
@@ -179,11 +178,11 @@ sha256 <- function(x, key = NULL, convert = TRUE, file)
 #' # SipHash-1-3 hash as raw vector:
 #' siphash13("secret base", convert = FALSE)
 #' 
-#' # SipHash-2-4 hash using a character string key:
-#' siphash24("secret", key = "base")
+#' # SipHash-1-3 hash using a character string key:
+#' siphash13("secret", key = "base")
 #' 
-#' # SipHash-2-4 hash using a raw vector key:
-#' siphash24("secret", key = charToRaw("base"))
+#' # SipHash-1-3 hash using a raw vector key:
+#' siphash13("secret", key = charToRaw("base"))
 #' 
 #' # SipHash-1-3 hash a file:
 #' file <- tempfile(); cat("secret base", file = file)
@@ -195,10 +194,3 @@ sha256 <- function(x, key = NULL, convert = TRUE, file)
 siphash13 <- function(x, key = NULL, convert = TRUE, file)
   if (missing(file)) .Call(secretbase_siphash13, x, key, convert) else
     .Call(secretbase_siphash13_file, file, key, convert)
-
-#' @rdname siphash13
-#' @export
-#'
-siphash24 <- function(x, key = NULL, convert = TRUE, file)
-  if (missing(file)) .Call(secretbase_siphash24, x, key, convert) else
-    .Call(secretbase_siphash24_file, file, key, convert)
diff --git a/README.Rmd b/README.Rmd
index 4613d66..868b1e0 100644
--- a/README.Rmd
+++ b/README.Rmd
@@ -47,14 +47,16 @@ install.packages("secretbase", repos = "https://shikokuchuo.r-universe.dev")
 
 ### Quick Start
 
-#### SHA-3 and XOF usage:
+```{r secretbase}
+library(secretbase)
+```
+
+#### SHA-3
  
  - For the SHA-3 cryptographic hash algorithm, specify 'bits' as `224`, `256`, `384` or `512`
  - For the SHAKE256 extendable-output function (XOF), specify any other bit length
 
-```{r secretbase}
-library(secretbase)
-
+```{r sha3}
 sha3("secret base")
 
 sha3("secret base", convert = FALSE)
@@ -63,9 +65,10 @@ sha3("秘密の基地の中", bits = 512)
 
 ```
 
-#### Hash arbitrary R objects:
+#### Hash arbitrary R objects
 
- - Uses memory-efficient 'streaming' serialization, without allocation of the serialized object
+ - Character strings and raw vectors (without attributes) are hashed 'as is'
+ - Other objects are hashed using memory-efficient 'streaming' serialization, 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)
 
 ```{r streaming}
@@ -74,7 +77,7 @@ sha3(data.frame(a = 1, b = 2), bits = 160)
 sha3(NULL)
 ```
 
-#### Hash files:
+#### Hash files
 
  - Performed in a streaming fashion, accepting files larger than memory
 
@@ -86,7 +89,7 @@ sha3(file = file)
 unlink(file)
 ```
 
-#### Hash to integer:
+#### Hash to integer
 
  - Specify 'convert' as `NA` (and 'bits' as `32` for a single integer value)
  - May be supplied as deterministic random seeds for R's pseudo random number generators (RNGs)
@@ -99,24 +102,25 @@ sha3("秘密の基地の中", bits = 32, convert = NA)
 
 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. <sup>[2]</sup>
 
-#### Generating a SHA-256 HMAC:
+#### SHA-256
 
-- Use `sha256()` passing a character string or raw vector to 'key'.
+```{r sha256}
+sha256("secret base")
+```
+
+- For a SHA-256 HMAC, pass a character string or raw vector to 'key'
 
 ```{r hmac}
 sha256("secret base", key = "秘密の基地の中")
 ```
 
-#### Using SipHash:
+#### SipHash
 
-- SipHash is a fast, cryptographically-strong keyed hash.
-- Pass a character string or raw vector to 'key'. Up to 16 bytes (128 bits) of the key data is used.
-- SipHash-1-3 is optimized for performance; SipHash-2-4 recommended for security.
+- SipHash-1-3 is optimized for performance
+- Pass a character string or raw vector to 'key' - up to 16 bytes (128 bits) of the key data is used
 
 ```{r siphash}
 siphash13("secret base", key = charToRaw("秘密の基地の中"))
-
-siphash24("secret base", key = charToRaw("秘密の基地の中"))
 ```
 
 ### References
diff --git a/README.md b/README.md
index 0f23bbf..c4f218e 100644
--- a/README.md
+++ b/README.md
@@ -57,7 +57,11 @@ install.packages("secretbase", repos = "https://shikokuchuo.r-universe.dev")
 
 ### Quick Start
 
-#### SHA-3 and XOF usage:
+``` r
+library(secretbase)
+```
+
+#### SHA-3
 
 - For the SHA-3 cryptographic hash algorithm, specify ‘bits’ as `224`,
   `256`, `384` or `512`
@@ -65,8 +69,6 @@ install.packages("secretbase", repos = "https://shikokuchuo.r-universe.dev")
   bit length
 
 ``` r
-library(secretbase)
-
 sha3("secret base")
 #> [1] "a721d57570e7ce366adee2fccbe9770723c6e3622549c31c7cab9dbb4a795520"
 
@@ -78,10 +80,12 @@ sha3("秘密の基地の中", bits = 512)
 #> [1] "e30cdc73f6575c40d55b5edc8eb4f97940f5ca491640b41612e02a05f3e59dd9c6c33f601d8d7a8e2ca0504b8c22f7bc69fa8f10d7c01aab392781ff4ae1e610"
 ```
 
-#### Hash arbitrary R objects:
+#### Hash arbitrary R objects
 
-- Uses memory-efficient ‘streaming’ serialization, without allocation of
-  the serialized object
+- Character strings and raw vectors (without attributes) are hashed ‘as
+  is’
+- Other objects are hashed using memory-efficient ‘streaming’
+  serialization, 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)
@@ -94,7 +98,7 @@ sha3(NULL)
 #> [1] "b3e37e4c5def1bfb2841b79ef8503b83d1fed46836b5b913d7c16de92966dcee"
 ```
 
-#### Hash files:
+#### Hash files
 
 - Performed in a streaming fashion, accepting files larger than memory
 
@@ -104,7 +108,7 @@ sha3(file = file)
 #> [1] "a721d57570e7ce366adee2fccbe9770723c6e3622549c31c7cab9dbb4a795520"
 ```
 
-#### Hash to integer:
+#### Hash to integer
 
 - Specify ‘convert’ as `NA` (and ‘bits’ as `32` for a single integer
   value)
@@ -126,29 +130,29 @@ be especially suitable when first-best alternatives such as using
 recursive streams are too expensive or unable to preserve
 reproducibility. <sup>\[2\]</sup>
 
-#### Generating a SHA-256 HMAC:
+#### SHA-256
 
-- Use `sha256()` passing a character string or raw vector to ‘key’.
+``` r
+sha256("secret base")
+#> [1] "1951c1ca3d50e95e6ede2b1c26fefd0f0e8eba1e51a837f8ccefb583a2b686fe"
+```
+
+- For a SHA-256 HMAC, pass a character string or raw vector to ‘key’
 
 ``` r
 sha256("secret base", key = "秘密の基地の中")
 #> [1] "ec58099ab21325e792bef8f1aafc0a70e1a7227463cfc410931112705d753392"
 ```
 
-#### Using SipHash:
+#### SipHash
 
-- SipHash is a fast, cryptographically-strong keyed hash.
-- Pass a character string or raw vector to ‘key’. Up to 16 bytes (128
-  bits) of the key data is used.
-- SipHash-1-3 is optimized for performance; SipHash-2-4 recommended for
-  security.
+- SipHash-1-3 is optimized for performance
+- Pass a character string or raw vector to ‘key’ - up to 16 bytes (128
+  bits) of the key data is used
 
 ``` r
 siphash13("secret base", key = charToRaw("秘密の基地の中"))
 #> [1] "a1f0a751892cc7dd"
-
-siphash24("secret base", key = charToRaw("秘密の基地の中"))
-#> [1] "1bedfe817cac0562"
 ```
 
 ### References
diff --git a/man/siphash13.Rd b/man/siphash13.Rd
index 9899b51..fd73a78 100644
--- a/man/siphash13.Rd
+++ b/man/siphash13.Rd
@@ -2,12 +2,9 @@
 % Please edit documentation in R/base.R
 \name{siphash13}
 \alias{siphash13}
-\alias{siphash24}
 \title{SipHash Pseudorandom Function}
 \usage{
 siphash13(x, key = NULL, convert = TRUE, file)
-
-siphash24(x, key = NULL, convert = TRUE, file)
 }
 \arguments{
 \item{x}{object to hash. A character string or raw vector (without
@@ -35,9 +32,8 @@ A character string, raw or integer vector depending on 'convert'.
 }
 \description{
 Returns a fast, cryptographically-strong SipHash keyed hash of the supplied
-    object or file. SipHash-1-3 is optimised for performance, whereas
-    SipHash-2-4 is recommended for security. Note: SipHash is not a
-    cryptographic hash algorithm.
+    object or file. SipHash-1-3 is optimised for performance. Note: SipHash
+    is not a cryptographic hash algorithm.
 }
 \details{
 The SipHash family of cryptographically-strong pseudorandom
@@ -59,11 +55,11 @@ siphash13("secret base")
 # SipHash-1-3 hash as raw vector:
 siphash13("secret base", convert = FALSE)
 
-# SipHash-2-4 hash using a character string key:
-siphash24("secret", key = "base")
+# SipHash-1-3 hash using a character string key:
+siphash13("secret", key = "base")
 
-# SipHash-2-4 hash using a raw vector key:
-siphash24("secret", key = charToRaw("base"))
+# SipHash-1-3 hash using a raw vector key:
+siphash13("secret", key = charToRaw("base"))
 
 # SipHash-1-3 hash a file:
 file <- tempfile(); cat("secret base", file = file)
diff --git a/src/init.c b/src/init.c
index 412f5eb..c5031ad 100644
--- a/src/init.c
+++ b/src/init.c
@@ -25,8 +25,6 @@ static const R_CallMethodDef callMethods[] = {
   {"secretbase_sha256_file", (DL_FUNC) &secretbase_sha256_file, 3},
   {"secretbase_siphash13", (DL_FUNC) &secretbase_siphash13, 3},
   {"secretbase_siphash13_file", (DL_FUNC) &secretbase_siphash13_file, 3},
-  {"secretbase_siphash24", (DL_FUNC) &secretbase_siphash24, 3},
-  {"secretbase_siphash24_file", (DL_FUNC) &secretbase_siphash24_file, 3},
   {NULL, NULL, 0}
 };
 
diff --git a/src/secret.h b/src/secret.h
index a865eda..752d211 100644
--- a/src/secret.h
+++ b/src/secret.h
@@ -93,7 +93,6 @@ typedef struct secretbase_sha256_context {
 
 typedef struct secretbase_siphash_context {
   int skip;
-  unsigned N;
   CSipHash *ctx;
 } secretbase_siphash_context;
 
diff --git a/src/secret3.c b/src/secret3.c
index 758c4d4..a534102 100644
--- a/src/secret3.c
+++ b/src/secret3.c
@@ -107,7 +107,7 @@ void c_siphash_init_nokey(CSipHash *state) {
   
 }
 
-static inline void c_siphash_append_N(CSipHash *state, const uint8_t *bytes, size_t n_bytes, unsigned N) {
+static inline void c_siphash_append(CSipHash *state, const uint8_t *bytes, size_t n_bytes) {
   
   const uint8_t *end = bytes + n_bytes;
   size_t left = state->n_bytes & 7;
@@ -123,8 +123,7 @@ static inline void c_siphash_append_N(CSipHash *state, const uint8_t *bytes, siz
       return;
     
     state->v3 ^= state->padding;
-    for (unsigned i = 0; i < N; i++)
-      c_siphash_sipround(state);
+    c_siphash_sipround(state);
     state->v0 ^= state->padding;
     
     state->padding = 0;
@@ -136,8 +135,7 @@ static inline void c_siphash_append_N(CSipHash *state, const uint8_t *bytes, siz
     m = c_siphash_read_le64(bytes);
     
     state->v3 ^= m;
-    for (unsigned i = 0; i < N; i++)
-      c_siphash_sipround(state);
+    c_siphash_sipround(state);
     state->v0 ^= m;
   }
 
@@ -163,20 +161,19 @@ static inline void c_siphash_append_N(CSipHash *state, const uint8_t *bytes, siz
   
 }
 
-static inline uint64_t c_siphash_finalize_NM(CSipHash *state, unsigned N, unsigned M) {
+static inline uint64_t c_siphash_finalize(CSipHash *state) {
   
   uint64_t b;
   
   b = state->padding | (((uint64_t) state->n_bytes) << 56);
   
   state->v3 ^= b;
-  for (unsigned i = 0; i < N; i++)
-    c_siphash_sipround(state);
+  c_siphash_sipround(state);
   state->v0 ^= b;
   
   state->v2 ^= 0xff;
   
-  for (unsigned i = 0; i < M; i++)
+  for (unsigned i = 0; i < 3; i++)
     c_siphash_sipround(state);
   
   return state->v0 ^ state->v1 ^ state->v2  ^ state->v3;
@@ -188,11 +185,11 @@ static inline uint64_t c_siphash_finalize_NM(CSipHash *state, unsigned N, unsign
 static void hash_bytes(R_outpstream_t stream, void *src, int len) {
   
   secretbase_siphash_context *sctx = (secretbase_siphash_context *) stream->data;
-  sctx->skip ? (void) sctx->skip-- : c_siphash_append_N(sctx->ctx, (uint8_t *) src, (size_t) len, sctx->N);
+  sctx->skip ? (void) sctx->skip-- : c_siphash_append(sctx->ctx, (uint8_t *) src, (size_t) len);
   
 }
 
-static void hash_file(CSipHash *ctx, const SEXP x, const unsigned N) {
+static void hash_file(CSipHash *ctx, const SEXP x) {
   
   if (TYPEOF(x) != STRSXP)
     Rf_error("'file' must be specified as a character string");
@@ -204,10 +201,8 @@ static void hash_file(CSipHash *ctx, const SEXP x, const unsigned N) {
   if ((f = fopen(file, "rb")) == NULL)
     Rf_error("file not found or no read permission at '%s'", file);
   
-  setbuf(f, NULL);
-  
   while ((cur = fread(buf, sizeof(char), SB_BUF_SIZE, f))) {
-    c_siphash_append_N(ctx, buf, cur, N);
+    c_siphash_append(ctx, buf, cur);
   }
   
   if (ferror(f)) {
@@ -218,19 +213,19 @@ static void hash_file(CSipHash *ctx, const SEXP x, const unsigned N) {
   
 }
 
-static void hash_object(CSipHash *ctx, const SEXP x, const unsigned N) {
+static void hash_object(CSipHash *ctx, const SEXP x) {
   
   switch (TYPEOF(x)) {
   case STRSXP:
     if (XLENGTH(x) == 1 && ATTRIB(x) == R_NilValue) {
       const char *s = CHAR(STRING_ELT(x, 0));
-      c_siphash_append_N(ctx, (uint8_t *) s, strlen(s), N);
+      c_siphash_append(ctx, (uint8_t *) s, strlen(s));
       return;
     }
     break;
   case RAWSXP:
     if (ATTRIB(x) == R_NilValue) {
-      c_siphash_append_N(ctx, (uint8_t *) STDVEC_DATAPTR(x), (size_t) XLENGTH(x), N);
+      c_siphash_append(ctx, (uint8_t *) STDVEC_DATAPTR(x), (size_t) XLENGTH(x));
       return;
     }
     break;
@@ -238,7 +233,6 @@ static void hash_object(CSipHash *ctx, const SEXP x, const unsigned N) {
   
   secretbase_siphash_context sctx;
   sctx.skip = SB_SERIAL_HEADERS;
-  sctx.N = N;
   sctx.ctx = ctx;
   
   struct R_outpstream_st output_stream;
@@ -257,8 +251,7 @@ static void hash_object(CSipHash *ctx, const SEXP x, const unsigned N) {
 }
 
 static SEXP secretbase_siphash_impl(const SEXP x, const SEXP key, const SEXP convert,
-                                    void (*const hash_func)(CSipHash *, SEXP, unsigned),
-                                    const unsigned N, const unsigned M) {
+                                    void (*const hash_func)(CSipHash *, SEXP)) {
   
   const int conv = LOGICAL(convert)[0];
   uint64_t hash;
@@ -286,9 +279,8 @@ static SEXP secretbase_siphash_impl(const SEXP x, const SEXP key, const SEXP con
     memcpy(seed, data, klen < SB_SKEY_SIZE ? klen : SB_SKEY_SIZE);
     c_siphash_init(&ctx, seed);
   }
-  hash_func(&ctx, x, N);
-  hash = c_siphash_finalize_NM(&ctx, N, M);
-  clear_buffer(&ctx, sizeof(CSipHash));
+  hash_func(&ctx, x);
+  hash = c_siphash_finalize(&ctx);
   
   return hash_to_sexp((unsigned char *) &hash, SB_SIPH_SIZE, conv);
   
@@ -298,24 +290,12 @@ static SEXP secretbase_siphash_impl(const SEXP x, const SEXP key, const SEXP con
 
 SEXP secretbase_siphash13(SEXP x, SEXP key, SEXP convert) {
   
-  return secretbase_siphash_impl(x, key, convert, hash_object, 1u, 3u);
+  return secretbase_siphash_impl(x, key, convert, hash_object);
   
 }
 
 SEXP secretbase_siphash13_file(SEXP x, SEXP key, SEXP convert) {
   
-  return secretbase_siphash_impl(x, key, convert, hash_file, 1u, 3u);
-  
-}
-
-SEXP secretbase_siphash24(SEXP x, SEXP key, SEXP convert) {
-  
-  return secretbase_siphash_impl(x, key, convert, hash_object, 2u, 4u);
-  
-}
-
-SEXP secretbase_siphash24_file(SEXP x, SEXP key, SEXP convert) {
-  
-  return secretbase_siphash_impl(x, key, convert, hash_file, 2u, 4u);
+  return secretbase_siphash_impl(x, key, convert, hash_file);
   
 }
diff --git a/tests/tests.R b/tests/tests.R
index 7b821ff..f2168d0 100644
--- a/tests/tests.R
+++ b/tests/tests.R
@@ -70,11 +70,9 @@ test_equal(sha256("secret base", key = character()), "6bc4693e2025baadf345dd0b13
 test_error(sha256("secret base", key = list()), "'key' must be a character string, raw vector or NULL")
 # SipHash tests:
 test_equal(siphash13(""), "2c530c1562a7fbd1")
-test_equal(siphash24(""), "d70077739d4b921e")
 test_equal(siphash13("", key = ""), "2c530c1562a7fbd1")
 test_equal(siphash13("", key = character()), "2c530c1562a7fbd1")
 test_equal(siphash13("secret base"), "48c60a316babef0e")
-test_equal(siphash24("secret base"), "bdb6899a934fdf5a")
 test_equal(siphash13("secret base", key = "secret base"), "2cf27a8f22f02e59")
 test_equal(siphash13("secret base", key = c("secret base", "more")), "2cf27a8f22f02e59")
 test_equal(siphash13("secret base", key = as.raw(1L)), "5ecd894f7d269521")
@@ -88,14 +86,12 @@ test_equal(siphash13(NULL), "08d5f59e833de599")
 test_equal(siphash13(substitute()), "c8cadc1ab377142a")
 test_equal(siphash13(`class<-`(siphash13(character(), convert = FALSE), "hash")), "39124d8b9643418a") 
 test_error(siphash13(file = NULL), "'file' must be specified as a character string")
-hash_func <- function(file, string, func) {
+hash_func <- function(file, string) {
   on.exit(unlink(file))
   cat(string, file = file)
-  func(file = file)
+  siphash13(file = file)
 }
-test_equal(hash_func(tempfile(), "secret base", siphash13), "48c60a316babef0e")
-test_equal(hash_func(tempfile(), "secret base", siphash24), "bdb6899a934fdf5a")
-test_error(hash_func("", "", siphash13), "file not found or no read permission")
-test_error(hash_func("", "", siphash24), "file not found or no read permission")
+test_equal(hash_func(tempfile(), "secret base"), "48c60a316babef0e")
+test_error(hash_func("", ""), "file not found or no read permission")
 if (.Platform[["OS.type"]] == "unix") test_error(siphash13(file = "~/"), "file read error")
 test_equal(siphash13(paste(1:888, collapse = "")), "8337f50b05209c40")