diff --git a/LICENSES/Unlicense.txt b/LICENSES/Unlicense.txt
new file mode 100644
index 0000000..5227a51
--- /dev/null
+++ b/LICENSES/Unlicense.txt
@@ -0,0 +1,22 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute
+this software, either in source code form or as a compiled binary, for any
+purpose, commercial or non-commercial, and by any means.
+
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and
+to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of relinquishment
+in perpetuity of all present and future rights to this software under copyright
+law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
+THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to
diff --git a/SHA256SUMS.sources b/SHA256SUMS.sources
index 3608aee..7d709c0 100644
--- a/SHA256SUMS.sources
+++ b/SHA256SUMS.sources
@@ -17,3 +17,4 @@ ecb5c6469d732bcf01d6ec1afe9e64f1668caba5bfdb103c28d7f537ba3cdb8a patch-2.5.9.ta
9fa29beb2fc4a3c373829fc051830796de301f32a719d0b52a400d1719bbd7b1 perl-5.003.tar.gz
1184478b298978b164a383ed5661e3a117c48ab97d6d0ab7ef614cdbe918b9eb perl5.004_05.tar.gz
c6c37e888b136ccefab903c51149f4b7bd659d69d4aea21245f61053a57aa60a tar-1.12.tar.gz
+404a8d72427a559c074e581bf8f7d5a73283faf249cd3faf6dc1c6faf97d07c7 sha-2-61555d.tar.gz
diff --git a/rootfs.sh b/rootfs.sh
index 3454705..4667e35 100755
--- a/rootfs.sh
+++ b/rootfs.sh
@@ -148,6 +148,9 @@ get_file https://ftp.gnu.org/gnu/gzip/gzip-1.2.4.tar 1
# patch 2.5.9
get_file https://ftp.gnu.org/pub/gnu/patch/patch-2.5.9.tar.gz 1
+# sha-2 61555d
+get_file https://github.com/amosnier/sha-2/archive/61555d.tar.gz 1 sha-2-61555d.tar.gz
+
# make 3.80
get_file https://ftp.gnu.org/gnu/make/make-3.80.tar.gz 1
diff --git a/sysa/after.kaem.run b/sysa/after.kaem.run
index b8b568f..fb136ae 100755
--- a/sysa/after.kaem.run
+++ b/sysa/after.kaem.run
@@ -86,41 +86,47 @@ cd ${pkg}
kaem --file ${pkg}.kaem
cd ..
-# Part 12: mes-libc-patched
+# Part 12: sha-2
+pkg="sha-2-61555d"
+cd ${pkg}
+kaem --file ${pkg}.kaem
+cd ..
+
+# Part 13: mes-libc-patched
cd tcc-0.9.27
kaem --file mes-libc-patched.kaem
cd ..
-# Part 13: tcc-patched
+# Part 14: tcc-patched
cd tcc-0.9.27
kaem --file tcc-patched.kaem
cd ..
-# Part 14: make
+# Part 15: make
pkg="make-3.80"
cd ${pkg}
kaem --file ${pkg}.kaem
cd ..
-# Part 15: bzip2
+# Part 16: bzip2
pkg="bzip2-1.0.8"
cd ${pkg}
kaem --file ${pkg}.kaem
cd ..
-# Part 16: coreutils
+# Part 17: coreutils
pkg="coreutils-5.0"
cd ${pkg}
kaem --file ${pkg}.kaem
cd ..
-# Part 17: heirloom-devtools
+# Part 18: heirloom-devtools
pkg="heirloom-devtools-070527"
cd ${pkg}
kaem --file ${pkg}.kaem
cd ..
-# Part 18: bash
+# Part 19: bash
pkg="bash-2.05b"
cd ${pkg}
kaem --file ${pkg}.kaem
diff --git a/sysa/run.sh b/sysa/run.sh
index c545ed1..4c58023 100755
--- a/sysa/run.sh
+++ b/sysa/run.sh
@@ -9,36 +9,36 @@ set -e
export PREFIX=/after
-# Part 19
+# Part 20
build flex-2.5.11
-# Part 20
+# Part 21
build musl-1.1.24
-# Part 21
-build tcc-0.9.27 tcc-musl.sh
-
# Part 22
-build m4-1.4.7
+build tcc-0.9.27 tcc-musl.sh checksums/tcc-musl
# Part 23
-build flex-2.6.4
+build m4-1.4.7
# Part 24
+build flex-2.6.4
+
+# Part 25
build bison-3.4.1 stage1.sh
build bison-3.4.1 stage2.sh
build bison-3.4.1 stage3.sh
-# Part 25
+# Part 26
build grep-2.4
-# Part 26
+# Part 27
build diffutils-2.7
-# Part 27
+# Part 28
build coreutils-5.0
-# Part 28
+# Part 29
build gawk-3.0.4
# Part 29
diff --git a/sysa/sha-2-61555d/checksums b/sysa/sha-2-61555d/checksums
new file mode 100644
index 0000000..4c9c42d
--- /dev/null
+++ b/sysa/sha-2-61555d/checksums
@@ -0,0 +1 @@
+53384 /after/bin/sha256sum
diff --git a/sysa/sha-2-61555d/patches/frontend.patch b/sysa/sha-2-61555d/patches/frontend.patch
new file mode 100644
index 0000000..706e531
--- /dev/null
+++ b/sysa/sha-2-61555d/patches/frontend.patch
@@ -0,0 +1,151 @@
+SPDX-FileCopyrightText: 2021 Bastian Bittorf
+SPDX-FileCopyrightText: 2021 fosslinux
+
+SPDX-License-Identifier: Unlicense
+
+This adds a main() function to this tool, giving a frontend so we can call
+it from the command line.
+
+--- sha-256.c 2019-08-04 22:20:53.000000000 +1000
++++ sha-256.c 2021-02-15 17:21:27.478945543 +1100
+@@ -1,10 +1,16 @@
+ #include
+ #include
+-
+-#include "sha-256.h"
++#include
+
+ #define CHUNK_SIZE 64
+ #define TOTAL_LEN_LEN 8
++#define MAX_FILE_SIZE 2*1024*1024
++
++void show_usage(void)
++{
++ printf("Usage: sha256sum \n");
++ printf(" sha256sum -c \n");
++}
+
+ /*
+ * ABOUT bool: this file does not use bool in order to be as pre-C99 compatible as possible.
+@@ -217,3 +223,121 @@
+ hash[j++] = (uint8_t) h[i];
+ }
+ }
++
++static void hash_to_string(char hash_string[66], uint8_t hash[32])
++{
++ for (size_t i = 0; i < 32; i++) {
++ hash_string += sprintf(hash_string, "%02x", hash[i]);
++ }
++ hash_string[65] = '\0';
++}
++
++static void hash_as_string(char filename[128], char hash_string[66])
++{
++ char buffer[MAX_FILE_SIZE];
++
++ FILE* fp = fopen(filename, "r");
++ if (fp == NULL)
++ {
++ printf("Opening file %s failed!", filename);
++ hash_string = NULL;
++ return;
++ }
++
++ size_t i;
++ for (i = 0; i < MAX_FILE_SIZE; i++) {
++ int c = fgetc(fp);
++ if (c == EOF) {
++ break;
++ }
++ buffer[i] = c;
++ }
++
++ uint8_t hash[32];
++
++ calc_sha_256(hash, buffer, i);
++ hash_to_string(hash_string, hash);
++}
++
++int main(int argc, char **argv)
++{
++ char buffer[MAX_FILE_SIZE];
++ size_t i;
++ FILE *fp;
++ FILE *csum_fp;
++
++ if (argc == 1) {
++ show_usage();
++ return 2;
++ }
++
++ if ((strcmp(argv[1], "-c") == 0) || (strcmp(argv[1], "--check") == 0)) {
++ /* Operate in check mode */
++ int failed = 0;
++
++ /* Get and open checksum file */
++ char *csum_filename = argv[2];
++ csum_fp = fopen(csum_filename, "r");
++ if (csum_fp == NULL) {
++ printf("Opening file %s failed!", csum_filename);
++ };
++
++ /* We break out of this loop at EOF */
++ while (1) {
++ /* Get the hash we need to check against */
++ char hash_true[256];
++ char filename[512];
++ int c = fgetc(csum_fp);
++ i = 0;
++ while (c != ' ' && c != EOF) {
++ hash_true[i] = c;
++ c = fgetc(csum_fp);
++ i++;
++ }
++ if(c == EOF) break;
++ /* Skip the next space(s) */
++ while (c == ' ') {
++ c = fgetc(csum_fp);
++ }
++ if(c == EOF) break;
++ /* Get the filename */
++ i = 0;
++ while (c != '\n' && c != EOF) {
++ filename[i] = c;
++ c = fgetc(csum_fp);
++ i++;
++ }
++ filename[i] = '\0';
++
++ /* Break out @ EOF */
++ if (c == EOF) break;
++
++ /* Get the hash */
++ char hash_string[66];
++ hash_as_string(filename, hash_string);
++ if (hash_string == NULL) return 127;
++
++ /* Output results */
++ printf("%s: ", filename);
++ if (strcmp(hash_true, hash_string)) {
++ printf("FAILED\n");
++ failed = 1;
++ } else {
++ printf("OK\n");
++ }
++ }
++
++ if (failed) return 1;
++ } else {
++ /* All the arguments are files to generate checksums for */
++
++ for (i = 1; i < argc; i++) {
++ char hash[66];
++ hash_as_string(argv[i], hash);
++ if (hash == NULL) return 127;
++ printf("%s %s\n", hash, argv[i]);
++ }
++ }
++
++ return 0;
++}
diff --git a/sysa/sha-2-61555d/sha-2-61555d.kaem b/sysa/sha-2-61555d/sha-2-61555d.kaem
new file mode 100755
index 0000000..0a9a642
--- /dev/null
+++ b/sysa/sha-2-61555d/sha-2-61555d.kaem
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+# SPDX-FileCopyrightText: 2021 fosslinux
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set -ex
+
+cd build
+
+# Extract
+gunzip ../src/${pkg}.tar.gz
+tar xf ../src/${pkg}.tar
+cd sha-2-61555d45676473e77c11f8da97301e2d2b865871
+
+# Patch
+patch -Np0 -i ../../patches/frontend.patch
+
+# Compile
+tcc -c -o sha-256.o sha-256.c
+
+# Link
+tcc -static -o ${bindir}/sha256sum sha-256.o
+
+# No test avaliable
+
+cd ../..
+
+# Checksums
+fletcher16 checksums