diff --git a/implementations/rust/preserves/src/hex.rs b/implementations/rust/preserves/src/hex.rs
new file mode 100644
index 0000000..2d0f1d3
--- /dev/null
+++ b/implementations/rust/preserves/src/hex.rs
@@ -0,0 +1,126 @@
+pub enum HexParser {
+    Liberal,
+    WhitespaceAllowed,
+    Strict,
+}
+
+pub enum HexFormatter {
+    Lines(usize),
+    Packed,
+}
+
+pub fn hexdigit(v: u8) -> char {
+    (if v < 10 {('0' as u8) + v} else {('a' as u8) + v - 10}) as char
+}
+
+pub fn unhex(c: char) -> Option<u8> {
+    if c >= '0' && c <= '9' {
+        return Some((c as u8) - ('0' as u8));
+    }
+    if c >= 'a' && c <= 'f' {
+        return Some((c as u8) - ('a' as u8) + 10);
+    }
+    if c >= 'A' && c <= 'F' {
+        return Some((c as u8) - ('A' as u8) + 10);
+    }
+    None
+}
+
+impl HexParser {
+    pub fn decode(&self, s: &str) -> Option<Vec<u8>> {
+        let mut result = Vec::new();
+        let mut buf: u8 = 0;
+        let mut buf_full = false;
+        for c in s.chars() {
+            match unhex(c) {
+                None =>
+                    match self {
+                        HexParser::Liberal => (),
+                        HexParser::WhitespaceAllowed => if !c.is_whitespace() { return None },
+                        HexParser::Strict => return None,
+                    },
+                Some(nibble) =>
+                    if buf_full {
+                        result.push(buf << 4 | nibble);
+                        buf_full = false;
+                    } else {
+                        buf = nibble;
+                        buf_full = true;
+                    },
+            }
+        }
+        Some(result)
+    }
+}
+
+impl HexFormatter {
+    pub fn encode(&self, bs: &[u8]) -> String {
+        match self {
+            HexFormatter::Lines(max_line_length) => {
+                let mut lines = Vec::new();
+                let mut line = String::new();
+                for b in bs {
+                    if line.len() + 2 > *max_line_length {
+                        lines.push(std::mem::take(&mut line));
+                    }
+                    line.push(hexdigit(b >> 4));
+                    line.push(hexdigit(b & 15));
+                }
+                lines.push(std::mem::take(&mut line));
+                lines.join("\n")
+            }
+            HexFormatter::Packed => {
+                let mut result = String::new();
+                for b in bs {
+                    result.push(hexdigit(b >> 4));
+                    result.push(hexdigit(b & 15));
+                }
+                result
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test] fn test_decode_packed() {
+        let s = "01ab00ff";
+        assert_eq!(HexParser::Strict.decode(s), Some(vec![1, 171, 0, 255]));
+        assert_eq!(HexParser::WhitespaceAllowed.decode(s), Some(vec![1, 171, 0, 255]));
+        assert_eq!(HexParser::Liberal.decode(s), Some(vec![1, 171, 0, 255]));
+    }
+
+    #[test] fn test_decode_whitespace() {
+        let s = "01ab  00ff";
+        assert_eq!(HexParser::Strict.decode(s), None);
+        assert_eq!(HexParser::WhitespaceAllowed.decode(s), Some(vec![1, 171, 0, 255]));
+        assert_eq!(HexParser::Liberal.decode(s), Some(vec![1, 171, 0, 255]));
+    }
+
+    #[test] fn test_decode_liberal() {
+        let s = "01ab zz 00ff";
+        assert_eq!(HexParser::Strict.decode(s), None);
+        assert_eq!(HexParser::WhitespaceAllowed.decode(s), None);
+        assert_eq!(HexParser::Liberal.decode(s), Some(vec![1, 171, 0, 255]));
+    }
+
+    #[test] fn test_encode_lines() {
+        assert_eq!(HexFormatter::Lines(10).encode(&vec![0x5a; 11]), "5a5a5a5a5a\n5a5a5a5a5a\n5a");
+        assert_eq!(HexFormatter::Lines(10).encode(&vec![0x5a; 10]), "5a5a5a5a5a\n5a5a5a5a5a");
+        assert_eq!(HexFormatter::Lines(10).encode(&vec![0x5a;  9]), "5a5a5a5a5a\n5a5a5a5a");
+        assert_eq!(HexFormatter::Lines(9).encode(&vec![0x5a; 11]), "5a5a5a5a\n5a5a5a5a\n5a5a5a");
+        assert_eq!(HexFormatter::Lines(9).encode(&vec![0x5a; 10]), "5a5a5a5a\n5a5a5a5a\n5a5a");
+        assert_eq!(HexFormatter::Lines(9).encode(&vec![0x5a;  9]), "5a5a5a5a\n5a5a5a5a\n5a");
+        assert_eq!(HexFormatter::Lines(8).encode(&vec![0x5a; 11]), "5a5a5a5a\n5a5a5a5a\n5a5a5a");
+        assert_eq!(HexFormatter::Lines(8).encode(&vec![0x5a; 10]), "5a5a5a5a\n5a5a5a5a\n5a5a");
+        assert_eq!(HexFormatter::Lines(8).encode(&vec![0x5a;  9]), "5a5a5a5a\n5a5a5a5a\n5a");
+    }
+
+    #[test] fn test_encode_packed() {
+        assert_eq!(HexFormatter::Packed.encode(&vec![0x5a; 11]), "5a5a5a5a5a5a5a5a5a5a5a");
+        assert_eq!(HexFormatter::Packed.encode(&vec![0x5a; 10]), "5a5a5a5a5a5a5a5a5a5a");
+        assert_eq!(HexFormatter::Packed.encode(&vec![0x5a;  9]), "5a5a5a5a5a5a5a5a5a");
+    }
+}
diff --git a/implementations/rust/preserves/src/lib.rs b/implementations/rust/preserves/src/lib.rs
index 85e4b46..38aeb2e 100644
--- a/implementations/rust/preserves/src/lib.rs
+++ b/implementations/rust/preserves/src/lib.rs
@@ -1,6 +1,7 @@
 pub mod de;
-pub mod ser;
 pub mod error;
+pub mod hex;
+pub mod ser;
 pub mod set;
 pub mod symbol;
 pub mod value;