diff --git a/set1/challenge5_repeating_xor/5.txt b/set1/challenge5_repeating_xor/5.txt
new file mode 100644
index 0000000..ad63bd8
--- /dev/null
+++ b/set1/challenge5_repeating_xor/5.txt
@@ -0,0 +1,2 @@
+Burning 'em, if you ain't quick and nimble
+I go crazy when I hear a cymbal
diff --git a/set1/challenge5_repeating_xor/build.zig b/set1/challenge5_repeating_xor/build.zig
new file mode 100644
index 0000000..1c13e58
--- /dev/null
+++ b/set1/challenge5_repeating_xor/build.zig
@@ -0,0 +1,27 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard release options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
+    const mode = b.standardReleaseOptions();
+
+    const exe = b.addExecutable("challenge5_repeating_xor", "src/main.zig");
+    exe.setTarget(target);
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const run_cmd = exe.run();
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+}
diff --git a/set1/challenge5_repeating_xor/src/main.zig b/set1/challenge5_repeating_xor/src/main.zig
new file mode 100644
index 0000000..5d5bac4
--- /dev/null
+++ b/set1/challenge5_repeating_xor/src/main.zig
@@ -0,0 +1,21 @@
+const std = @import("std");
+
+pub fn main() anyerror!void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
+    const stdout = std.io.getStdOut().writer();
+
+    const key = "ICE";
+    const input = try stdin.readAllAlloc(allocator, 4096);
+    defer allocator.free(input);
+
+    var i: usize = 0;
+    for (input) |*char| {
+        char.* ^= key[i];
+        i = (i + 1) % key.len;
+    }
+
+    try stdout.print("{s}\n", .{std.fmt.fmtSliceHexLower(input)});
+}