diff --git a/src/bin/sol_cli.rs b/src/bin/sol_cli.rs
index 45435d9..f85972b 100644
--- a/src/bin/sol_cli.rs
+++ b/src/bin/sol_cli.rs
@@ -29,7 +29,7 @@ fn main() {
         let board = if let Some(board_string) = args.solve_board {
             Board::from_string(board_string)
         } else if let Some(board_id) = args.solve {
-            Board::from_id(board_id)
+            Board::from_id(&board_id)
         } else {
             println!("Use --help to see available options");
             return;
@@ -106,7 +106,7 @@ struct Args {
 
     #[argh(option, short = 's')]
     /// the id of the board to solve
-    solve: Option<u128>,
+    solve: Option<String>,
 
     #[argh(option)]
     /// the board to solve in board representation
diff --git a/src/board.rs b/src/board.rs
index d09fa47..6505b22 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -17,6 +17,8 @@ use errors::SError;
 use piece::Piece;
 use square::{Square, SquarePair};
 
+use crate::util;
+
 #[derive(Clone)]
 pub struct Board {
     pub cells: [[Option<Piece>; BOARD_SIZE]; BOARD_SIZE],
@@ -43,12 +45,20 @@ impl Board {
         }
     }
 
-    pub fn from_id(board_id: u128) -> Result<Self, SError> {
+    pub fn from_id(board_id: &str) -> Result<Self, SError> {
+        let mut board_id_bytes = [0; 8];
+        board_id_bytes.copy_from_slice(board_id.as_bytes());
+        let mut working_bytes_slice = [0; 6];
+        util::b64_decode_48(&board_id_bytes, &mut working_bytes_slice);
+
+        let mut working_bytes = [0; 8];
+        working_bytes[2..].copy_from_slice(&working_bytes_slice);
+        let mut working = u64::from_be_bytes(working_bytes);
+
         let mut board = Board::new();
-        let mut working = board_id;
+        let mask = 0b111;
         for i in (0..BOARD_SIZE).rev() {
             for j in (0..BOARD_SIZE).rev() {
-                let mask = 0b111;
                 let piece = Board::get_piece_from_encoding((working & mask) as u8);
                 working = working >> 3;
                 let piece = piece?;
@@ -136,21 +146,24 @@ impl Board {
 
     pub fn pretty_print(&self) {
         println!("{}", self.print(true));
+        // println!("{:^40}\n", format!("id: {:#018x}", self.id()));
         println!("{:^40}\n", format!("id: {}", self.id()));
     }
 
-    pub fn id(&self) -> u128 {
-        let mut res: u128 = 0;
+    pub fn id(&self) -> String {
+        let mut res: u64 = 0;
 
         for i in 0..BOARD_SIZE {
             for j in 0..BOARD_SIZE {
                 res = res << 3;
                 let byte = Board::get_piece_encoding(self.cells[i][j]);
-                res = res | byte as u128
+                res = res | byte as u64
             }
         }
 
-        res
+        let mut id_bytes = [0; 6];
+        id_bytes.copy_from_slice(&res.to_be_bytes()[2..]);
+        util::b64_encode_48(&id_bytes)
     }
 
     fn print(&self, pretty: bool) -> String {
@@ -585,7 +598,7 @@ mod tests {
         board.set(sq!("Nc4"));
 
         let id = board.id();
-        let board2 = Board::from_id(id);
+        let board2 = Board::from_id(&id);
         let board2 = board2.unwrap();
 
         validate_board!(board2, "..NB", "....", "RQ.K", "P...");
diff --git a/src/lib.rs b/src/lib.rs
index be02fcd..f1f42dd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
 pub mod board;
 pub mod generator;
 pub mod solver;
+pub mod util;
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..0bf9a0a
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,44 @@
+pub(crate) fn b64_encode_48(input: &[u8; 6]) -> String {
+    let mut output = [0 as char; 8];
+    for (byte_chunk, output_slice) in input.chunks_exact(3).zip(output.chunks_exact_mut(4)) {
+        let byte1 = byte_chunk[0];
+        let byte2 = byte_chunk[1];
+        let byte3 = byte_chunk[2];
+
+        output_slice[0] = lookup((byte1 & 0b1111_1100) >> 2);
+        output_slice[1] = lookup((byte1 & 0b0000_0011) << 4 | (byte2 & 0b1111_0000) >> 4);
+        output_slice[2] = lookup((byte2 & 0b0000_1111) << 2 | (byte3 & 0b1100_0000) >> 6);
+        output_slice[3] = lookup(byte3 & 0b0011_1111);
+    }
+
+    output.iter().collect()
+}
+
+pub(crate) fn b64_decode_48(input: &[u8; 8], output: &mut [u8; 6]) {
+    for (char_chunk, output_slice) in input.chunks_exact(4).zip(output.chunks_exact_mut(3)) {
+        let char_1 = reverse_lookup(char_chunk[0] as char);
+        let char_2 = reverse_lookup(char_chunk[1] as char);
+        let char_3 = reverse_lookup(char_chunk[2] as char);
+        let char_4 = reverse_lookup(char_chunk[3] as char);
+
+        output_slice[0] = (char_1 << 2) | (char_2 >> 4);
+        output_slice[1] = (char_2 << 4) | (char_3 >> 2);
+        output_slice[2] = (char_3 << 6) | char_4;
+    }
+}
+
+const ALPHABET: &str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+fn lookup(idx: u8) -> char {
+    ALPHABET
+        .chars()
+        .nth(idx as usize)
+        .unwrap()
+}
+
+fn reverse_lookup(c: char) -> u8 {
+    ALPHABET
+        .chars()
+        .position(|x| x == c)
+        .unwrap() as u8
+}