4 files changed, 42 insertions, 21 deletions
diff --git a/src/lib/asn1/asn1_print.cpp b/src/lib/asn1/asn1_print.cpp
index 34c671483..1a1654fef 100644
--- a/src/lib/asn1/asn1_print.cpp
+++ b/src/lib/asn1/asn1_print.cpp
@@ -172,11 +172,7 @@ void ASN1_Formatter::decode(std::ostream& output,
             data.decode(number, ASN1_Type::Enumerated, class_tag);
             }
 
-         std::vector<uint8_t> rep = BigInt::encode(number);
-         if(rep.empty()) // if zero
-            rep.resize(1);
-
-         output << format(type_tag, class_tag, level, length, hex_encode(rep));
+         output << format(type_tag, class_tag, level, length, format_bn(number));
          }
       else if(type_tag == ASN1_Type::Boolean)
          {
@@ -324,4 +320,12 @@ std::string ASN1_Pretty_Printer::format_bin(ASN1_Type /*type_tag*/,
       return hex_encode(vec);
    }
 
+std::string ASN1_Pretty_Printer::format_bn(const BigInt& bn) const
+   {
+   if(bn.bits() < 16)
+      return bn.to_dec_string();
+   else
+      return bn.to_hex_string();
+   }
+
 }
diff --git a/src/lib/asn1/asn1_print.h b/src/lib/asn1/asn1_print.h
index 53ed42de6..94dc48d6a 100644
--- a/src/lib/asn1/asn1_print.h
+++ b/src/lib/asn1/asn1_print.h
@@ -14,6 +14,7 @@
 
 namespace Botan {
 
+class BigInt;
 class BER_Decoder;
 
 /**
@@ -58,13 +59,18 @@ class BOTAN_PUBLIC_API(2,4) ASN1_Formatter
 
       /**
       * This is called to format binary elements that we don't know how to
-      * convert to a string The result will be passed as value to format; the
+      * convert to a string. The result will be passed as value to format; the
       * tags are included as a hint to aid decoding.
       */
       virtual std::string format_bin(ASN1_Type type_tag,
                                      ASN1_Class class_tag,
                                      const std::vector<uint8_t>& vec) const = 0;
 
+      /**
+      * This is called to format integers
+      */
+      virtual std::string format_bn(const BigInt& bn) const = 0;
+
    private:
       void decode(std::ostream& output,
                   BER_Decoder& decoder,
@@ -114,6 +120,8 @@ class BOTAN_PUBLIC_API(2,4) ASN1_Pretty_Printer final : public ASN1_Formatter
                              ASN1_Class class_tag,
                              const std::vector<uint8_t>& vec) const override;
 
+      std::string format_bn(const BigInt& bn) const override;
+
       const size_t m_print_limit;
       const size_t m_print_binary_limit;
       const size_t m_initial_level;
diff --git a/src/lib/math/bigint/big_code.cpp b/src/lib/math/bigint/big_code.cpp
index 3ff31b639..c31221333 100644
--- a/src/lib/math/bigint/big_code.cpp
+++ b/src/lib/math/bigint/big_code.cpp
@@ -17,7 +17,10 @@ std::string BigInt::to_dec_string() const
    copy.set_sign(Positive);
 
    uint8_t remainder;
-   std::vector<uint8_t> digits;
+   secure_vector<uint8_t> digits;
+
+   // (over-)estimate of the number of digits, log2(10) ~= 3.32
+   digits.reserve(3.4 * this->bits());
 
    while(copy > 0)
       {
@@ -33,6 +36,9 @@ std::string BigInt::to_dec_string() const
 
    std::string s;
 
+   if(is_negative())
+      s += "-";
+
    for(auto i = digits.rbegin(); i != digits.rend(); ++i)
       {
       s.push_back(*i + '0');
@@ -46,11 +52,17 @@ std::string BigInt::to_dec_string() const
 
 std::string BigInt::to_hex_string() const
    {
-   const std::vector<uint8_t> bits = BigInt::encode(*this);
+   std::vector<uint8_t> bits = BigInt::encode(*this);
+
    if(bits.empty())
-      return "00";
-   else
-      return hex_encode(bits);
+      bits.push_back(0);
+
+   std::string hrep;
+   if(is_negative())
+      hrep += "-";
+   hrep += "0x";
+   hrep += hex_encode(bits);
+   return hrep;
    }
 
 /*
diff --git a/src/lib/math/bigint/big_io.cpp b/src/lib/math/bigint/big_io.cpp
index b31315eac..ae2855fcc 100644
--- a/src/lib/math/bigint/big_io.cpp
+++ b/src/lib/math/bigint/big_io.cpp
@@ -16,17 +16,17 @@ namespace Botan {
 */
 std::ostream& operator<<(std::ostream& stream, const BigInt& n)
    {
-   size_t base = 10;
-   if(stream.flags() & std::ios::hex)
-      base = 16;
-   if(stream.flags() & std::ios::oct)
+   const auto stream_flags = stream.flags();
+   if(stream_flags & std::ios::oct)
       throw Invalid_Argument("Octal output of BigInt not supported");
 
-   if(n == 0)
+   const size_t base = (stream_flags & std::ios::hex) ? 16 : 10;
+
+   if(n.is_zero())
       stream.write("0", 1);
    else
       {
-      if(n < 0)
+      if(n.is_negative())
          stream.write("-", 1);
 
       std::string enc;
@@ -36,10 +36,7 @@ std::ostream& operator<<(std::ostream& stream, const BigInt& n)
       else
          enc = n.to_hex_string();
 
-      size_t skip = 0;
-      while(skip < enc.size() && enc[skip] == '0')
-         ++skip;
-      stream.write(&enc[skip], enc.size() - skip);
+      stream.write(enc.data(), enc.size());
       }
    if(!stream.good())
       throw Stream_IO_Error("BigInt output operator has failed");