From 7aff2e1d279a4e442b32f49ca0a0eca065355787 Mon Sep 17 00:00:00 2001
From: murilo ijanc
Date: Wed, 25 Mar 2026 02:07:37 -0300
Subject: Initial commit: tesseras-paste decentralized pastebin

DHT-backed encrypted pastebin with two binaries (tp/tpd),
XChaCha20-Poly1305 encryption, content-addressed storage,
and Unix socket + HTTP interfaces.
---
 src/base58.rs | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 src/base58.rs

(limited to 'src/base58.rs')

diff --git a/src/base58.rs b/src/base58.rs
new file mode 100644
index 0000000..c412bc3
--- /dev/null
+++ b/src/base58.rs
@@ -0,0 +1,153 @@
+//! Bitcoin-style Base58 encoding/decoding.
+//!
+//! No external dependencies. Uses the standard Bitcoin
+//! alphabet (no 0, O, I, l to avoid ambiguity).
+
+const ALPHABET: &[u8; 58] =
+    b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+
+/// Decode table: ASCII byte → base58 value (255 = invalid).
+const DECODE: [u8; 128] = {
+    let mut table = [255u8; 128];
+    let mut i = 0;
+    while i < 58 {
+        table[ALPHABET[i] as usize] = i as u8;
+        i += 1;
+    }
+    table
+};
+
+/// Encode bytes to Base58 string.
+pub fn encode(input: &[u8]) -> String {
+    if input.is_empty() {
+        return String::new();
+    }
+
+    // Count leading zeros
+    let leading_zeros = input.iter().take_while(|&&b| b == 0).count();
+
+    // Convert to base58 via repeated division
+    let mut digits: Vec<u8> = Vec::with_capacity(input.len() * 2);
+    for &byte in input {
+        let mut carry = byte as u32;
+        for d in &mut digits {
+            carry += (*d as u32) << 8;
+            *d = (carry % 58) as u8;
+            carry /= 58;
+        }
+        while carry > 0 {
+            digits.push((carry % 58) as u8);
+            carry /= 58;
+        }
+    }
+
+    let mut result = String::with_capacity(leading_zeros + digits.len());
+    for _ in 0..leading_zeros {
+        result.push('1');
+    }
+    for &d in digits.iter().rev() {
+        result.push(ALPHABET[d as usize] as char);
+    }
+    result
+}
+
+/// Decode a Base58 string to bytes.
+pub fn decode(input: &str) -> Option<Vec<u8>> {
+    if input.is_empty() {
+        return Some(Vec::new());
+    }
+
+    // Count leading '1's (representing zero bytes)
+    let leading_ones = input.chars().take_while(|&c| c == '1').count();
+
+    // Convert from base58 via repeated multiplication
+    let mut bytes: Vec<u8> = Vec::with_capacity(input.len());
+    for c in input.chars() {
+        let c = c as usize;
+        if c >= 128 {
+            return None;
+        }
+        let val = DECODE[c];
+        if val == 255 {
+            return None;
+        }
+        let mut carry = val as u32;
+        for b in &mut bytes {
+            carry += (*b as u32) * 58;
+            *b = (carry & 0xFF) as u8;
+            carry >>= 8;
+        }
+        while carry > 0 {
+            bytes.push((carry & 0xFF) as u8);
+            carry >>= 8;
+        }
+    }
+
+    let mut result = vec![0; leading_ones];
+    result.extend(bytes.iter().rev());
+    Some(result)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn encode_empty() {
+        assert_eq!(encode(b""), "");
+    }
+
+    #[test]
+    fn encode_hello() {
+        assert_eq!(encode(b"Hello World"), "JxF12TrwUP45BMd");
+    }
+
+    #[test]
+    fn roundtrip() {
+        let data = b"tesseras-paste test data";
+        let encoded = encode(data);
+        let decoded = decode(&encoded).unwrap();
+        assert_eq!(decoded, data);
+    }
+
+    #[test]
+    fn roundtrip_binary() {
+        let data: Vec<u8> = (0..=255).collect();
+        let encoded = encode(&data);
+        let decoded = decode(&encoded).unwrap();
+        assert_eq!(decoded, data);
+    }
+
+    #[test]
+    fn leading_zeros() {
+        let data = [0, 0, 0, 1, 2, 3];
+        let encoded = encode(&data);
+        assert!(encoded.starts_with("111"));
+        let decoded = decode(&encoded).unwrap();
+        assert_eq!(decoded, data);
+    }
+
+    #[test]
+    fn decode_invalid_char() {
+        assert!(decode("invalid0char").is_none());
+    }
+
+    #[test]
+    fn decode_empty() {
+        assert_eq!(decode("").unwrap(), Vec::<u8>::new());
+    }
+
+    #[test]
+    fn known_vector() {
+        // SHA-256 of "test" in base58
+        let hash: [u8; 32] = {
+            use tesseras_dht::sha2::{Digest, Sha256};
+            let mut h = Sha256::new();
+            h.update(b"test");
+            h.finalize().into()
+        };
+        let encoded = encode(&hash);
+        let decoded = decode(&encoded).unwrap();
+        assert_eq!(decoded, hash);
+    }
+}
-- 
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