Index: build/test/test.tcl
==================================================================
--- build/test/test.tcl
+++ build/test/test.tcl
@@ -2,11 +2,11 @@
 
 lappend auto_path [file join [file dirname [info script]] .. ..]
 
 package require nano
 
-proc test1 {} {
+proc test_signatures {} {
 	# Detached signature
 	set data [binary decode hex 0000000000000000000000000000000000000000000000000000000000000000]
 	set key  [binary decode hex C4D214F19E706E9C7487CEF00DE8059200C32414F0ED82E5E33B523AEDF719BA]
 	set sig  [string toupper [binary encode hex [::nano::internal::signDetached $data $key]]]
 	set sig_expected 1C2DE9B8A71215F949A11BBEA7EFA4ECD67A8C2B5A9AD98AE6B1AB7F7A3D2CFD715F570309148C7B39C346FB9B91B321D7E75BD598F271AF31AB60A99D086709
@@ -48,8 +48,37 @@
 	if {$verified} {
 		puts "\[FAIL\] Got: $verified"
 		puts "\[FAIL\] Exp: false"
 		return false
 	}
+
+	return true
+}
+
+proc test_hashing {} {
+	# Basic test
+	set data [binary decode hex 4451686437A2BF5C4759100DE2ADE0F39B6877275AF997906B71B1A8EF1550A2]
+	set hash [binary encode hex [::nano::internal::hashData $data]]
+	set hash_expected "84ac733547d71c312e707508646008a9d8f84f7093e60ca91e4eb376365ac1921fdde6e8ccb3875ea12369d9f6fb02237f51f4c05f3555e57d11800deda7319f"
+	if {$hash ne $hash_expected} {
+		puts "\[FAIL\] Got: $hash"
+		puts "\[FAIL\] Exp: $hash_expected"
+
+		return false
+	}
+
+	return true
+}
+
+set tests {
+	signatures
+	hashing
+}
+
+foreach test $tests {
+	if {![test_$test]} {
+		puts "FAILED test $test"
+		exit 1
+	}
 }
 
-test1
+exit 0

Index: nano.c
==================================================================
--- nano.c
+++ nano.c
@@ -1,10 +1,11 @@
 #include <tcl.h>
 #include <stdint.h>
 #include <limits.h>
 #include <string.h>
 #include "tweetnacl.h"
+#include "blake2-supercop.h"
 
 #if 0
 #include <sys/random.h>
 
 void randombytes(uint8_t *buffer, uint64_t length) {
@@ -238,10 +239,31 @@
 	return(TCL_OK);
 
 	/* NOTREACH */
 	clientData = clientData;
 }
+
+static int nano_tcl_hash_data(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
+	unsigned char *data, result[crypto_sign_BYTES];
+	int data_length, result_length;
+
+	if (objc != 2) {
+		Tcl_WrongNumArgs(interp, 1, objv, "data");
+
+		return(TCL_ERROR);
+	}
+
+	data = Tcl_GetByteArrayFromObj(objv[1], &data_length);
+	crypto_hash(result, data, data_length);
+	result_length = sizeof(result);
+	Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(result, result_length));
+
+	return(TCL_OK);
+
+	/* NOTREACH */
+	clientData = clientData;
+}
 
 int Nano_Init(Tcl_Interp *interp) {
 #ifdef USE_TCL_STUBS
 	const char *tclInitStubs_ret;
 
@@ -253,8 +275,9 @@
 #endif
 
 	Tcl_CreateObjCommand(interp, "::nano::internal::signDetached", nano_tcl_sign_detached, NULL, NULL);
 	Tcl_CreateObjCommand(interp, "::nano::internal::publicKey", nano_tcl_secret_key_to_public_key, NULL, NULL);
 	Tcl_CreateObjCommand(interp, "::nano::internal::verifyDetached", nano_tcl_verify_detached, NULL, NULL);
+	Tcl_CreateObjCommand(interp, "::nano::internal::hashData", nano_tcl_hash_data, NULL, NULL);
 
 	return(TCL_OK);
 }