diff --git a/CMakeLists.txt b/CMakeLists.txt
index b443528..85b2586 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,7 @@ set(SOURCES
         src/string.c
         src/vector.c
         src/utility.c
+        src/crypto.c
 )
 
 if ((${CMAKE_SYSTEM_NAME} STREQUAL "Darwin"))
diff --git a/docs/crypto.md b/docs/crypto.md
new file mode 100644
index 0000000..cbcb855
--- /dev/null
+++ b/docs/crypto.md
@@ -0,0 +1,24 @@
+# crypto
+
+Cryptographic library
+
+## Functions
+
+### b64_encode
+
+Encodes an `unsigned char *` into base64. User is responsible for freeing the 
+`char *` that is returned.
+
+```c
+char *b64_encode(const unsigned char *s, size_t sz);
+```
+
+### b64_decode
+
+Decodes a base64 encoded set of bytes into an `unsigned char *`. User is responsible
+for freeing the `unsigned char *` that is returned. `decode_sz` is an optional argument
+in case you need to know the size of the decoded data, otherwise you can just pass `NULL`.
+
+```c
+unsigned char *b64_decode(const char *s, size_t sz, size_t *decode_sz);
+```
diff --git a/include/lfcrypto.h b/include/lfcrypto.h
new file mode 100644
index 0000000..a124336
--- /dev/null
+++ b/include/lfcrypto.h
@@ -0,0 +1,9 @@
+#ifndef LIBFLINT_CRYPTO_H
+#define LIBFLINT_CRYPTO_H
+
+#include <stddef.h>
+
+char *b64_encode(const unsigned char *s, size_t sz);
+unsigned char *b64_decode(const char *s, size_t sz, size_t *decode_sz);
+
+#endif // LIBFLINT_CRYPTO_H
diff --git a/mkdocs.yml b/mkdocs.yml
index 38d8c8c..7717dd6 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -7,6 +7,7 @@ nav:
   - 'Modules':
     - 'Binary Tree': 'binarytree.md'
     - 'Boolean': 'bool.md'
+    - 'Crypto': 'crypto.md'
     - 'Input': 'input.md'
     - 'Linked List': 'linkedlist.md'
     - 'Math': 'math.md'
diff --git a/src/crypto.c b/src/crypto.c
new file mode 100644
index 0000000..b7e5892
--- /dev/null
+++ b/src/crypto.c
@@ -0,0 +1,202 @@
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+#include "lfcrypto.h"
+
+#define B64_BUF_SZ (1024 * 64)
+
+static const char b64_table[] = {
+        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
+        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
+        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
+        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
+        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
+        'w', 'x', 'y', 'z', '0', '1', '2', '3',
+        '4', '5', '6', '7', '8', '9', '+', '/'
+};
+
+typedef struct {
+    char *ptr;
+    int count;
+} b64_buf;
+
+static int new_b64_buf(b64_buf *b) {
+    b->ptr = malloc(B64_BUF_SZ);
+    if (b->ptr == NULL) {
+        return 1;
+    }
+    b->count = 1;
+    return 0;
+}
+
+static int resize_b64_buf(b64_buf *b, size_t sz) {
+    if (sz > b->count * B64_BUF_SZ) {
+        while (sz > b->count * B64_BUF_SZ) {
+           b->count++;
+        }
+        b->ptr = realloc(b->ptr, B64_BUF_SZ * b->count);
+        if (b->ptr == NULL) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+char *b64_encode(const unsigned char *s, size_t sz) {
+    int i = 0;
+    b64_buf encbuf;
+    size_t size = 0;
+    unsigned char buf[4];
+    unsigned char tmp[3];
+
+    if (new_b64_buf(&encbuf) != 0) {
+        return NULL;
+    }
+
+    while (sz--) {
+        tmp[i++] = *(s++);
+        if (i == 3) {
+            buf[0] = (tmp[0] & 0xfc) >> 2;
+            buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
+            buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
+            buf[3] = tmp[2] & 0x3f;
+
+            if (resize_b64_buf(&encbuf, size + 4) != 0) {
+                free(encbuf.ptr);
+                return NULL;
+            }
+
+            for (i = 0; i < 4; ++i) {
+                encbuf.ptr[size++] = b64_table[buf[i]];
+            }
+
+            i = 0;
+        }
+    }
+
+    if (i > 0) {
+        for (int j = i; j < 3; ++j) {
+            tmp[j] = '\0';
+        }
+
+        buf[0] = (tmp[0] & 0xfc) >> 2;
+        buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
+        buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
+        buf[3] = tmp[2] & 0x3f;
+
+        for (int j = 0; (j < i + 1); ++j) {
+            if (resize_b64_buf(&encbuf, size + 1) != 0) {
+                free(encbuf.ptr);
+                return NULL;
+            }
+            encbuf.ptr[size++] = b64_table[buf[j]];
+        }
+
+        while (i++ < 3) {
+            if (resize_b64_buf(&encbuf, size + 1) != 0) {
+                free(encbuf.ptr);
+                return NULL;
+            }
+            encbuf.ptr[size++] = '=';
+        }
+    }
+
+    if (resize_b64_buf(&encbuf, size + 1) != 0) {
+        free(encbuf.ptr);
+        return NULL;
+    }
+    encbuf.ptr[size] = '\0';
+
+    return encbuf.ptr;
+}
+
+unsigned char *b64_decode(const char *s, size_t sz, size_t *decode_sz) {
+    int i = 0, j = 0, l = 0;
+    size_t size = 0;
+    b64_buf decbuf;
+    unsigned char buf[3];
+    unsigned char tmp[4];
+
+    if (new_b64_buf(&decbuf) != 0) {
+        return NULL;
+    }
+
+    while (sz--) {
+        if (s[j] == '=') {
+            break;
+        }
+        // Not base64 characters
+        if (!isalnum(s[j]) || s[j] == '+' || s[j] == '/') {
+            break;
+        }
+
+        tmp[i++] = s[j++];
+
+        if (i == 4) {
+            for (i = 0; i < 4; ++i) {
+                for (l = 0; l < 64; ++l) {
+                    if (tmp[i] == b64_table[l]) {
+                        tmp[i] = l;
+                        break;
+                    }
+                }
+            }
+
+            buf[0] = (tmp[0] << 2) + ((tmp[1] & 0x30) >> 4);
+            buf[1] = ((tmp[1] & 0xf) << 4) + ((tmp[2] & 0x3c) >> 2);
+            buf[2] = ((tmp[2] & 0x3) << 6) + tmp[3];
+
+            if (resize_b64_buf(&decbuf, size + 3) != 0) {
+                free(decbuf.ptr);
+                return NULL;
+            }
+
+            for (i = 0; i < 3; ++i) {
+                decbuf.ptr[size++] = buf[i];
+            }
+
+            i = 0;
+        }
+    }
+
+    if (i > 0) {
+        for (j = i; j < 4; ++j) {
+            tmp[j] = '\0';
+        }
+
+        for (j = 0; j < 4; ++j) {
+            for (l = 0; l < 64; ++l) {
+                if (tmp[j] == b64_table[l]) {
+                    tmp[j] = l;
+                    break;
+                }
+            }
+        }
+
+        buf[0] = (tmp[0] << 2) + ((tmp[1] & 0x30) >> 4);
+        buf[1] = ((tmp[1] & 0xf) << 4) + ((tmp[2] & 0x3c) >> 2);
+        buf[2] = ((tmp[2] & 0x3) << 6) + tmp[3];
+
+        if (resize_b64_buf(&decbuf, size + (i - 1)) != 0) {
+            free(decbuf.ptr);
+            return NULL;
+        }
+        for (j = 0; (j < i - 1); ++j) {
+            decbuf.ptr[size++] = buf[j];
+        }
+    }
+
+    if (resize_b64_buf(&decbuf, size + 1) != 0) {
+        free(decbuf.ptr);
+        return NULL;
+    }
+    decbuf.ptr[size] = '\0';
+
+    if (decode_sz != NULL) {
+        *decode_sz = size;
+    }
+
+    return (unsigned char*)decbuf.ptr;
+}
diff --git a/tests/tests.c b/tests/tests.c
index 04c2b95..a7164f6 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -10,6 +10,7 @@
 #include "lfvector.h"
 #include "lfmath.h"
 #include "lfstring.h"
+#include "lfcrypto.h"
 
 #if defined(__APPLE__) || defined(__MACH__)
 #include "lfmacos.h"
@@ -308,6 +309,25 @@ void test_string() {
     printf("Passes all string tests\n");
 }
 
+void test_crypto() {
+    char *in = "BUTT";
+    char *s = b64_encode(in, strlen(in));
+    assert(strcmp(s, "QlVUVA==") == 0);
+    free(s);
+
+    char *in2 = "a longer base64 test, apparently";
+    s = b64_encode(in2, strlen(in2));
+    assert(strcmp(s, "YSBsb25nZXIgYmFzZTY0IHRlc3QsIGFwcGFyZW50bHk=") == 0);
+    free(s);
+
+    char *out2 = "YSBsb25nZXIgYmFzZTY0IHRlc3QsIGFwcGFyZW50bHk=";
+    size_t s_sz = 0;
+    s = (char *)b64_decode(out2, strlen(out2), &s_sz);
+    assert(strcmp(s, "a longer base64 test, apparently") == 0);
+    assert(strlen(s) == s_sz);
+    free(s);
+}
+
 #if defined(__APPLE__) || defined(__MACH__)
 void test_macos() {
     printf("\n--- macOS TEST ---\n");
@@ -331,6 +351,7 @@ int main() {
     test_math();
     test_vector();
     test_string();
+    test_crypto();
 
 #if defined(__APPLE__) || defined(__MACH__)
     test_macos();