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Base64 is a freeware way of encoding 8-bit characters using only ASCII printable characters similar to UUENCODE. UUENCODE embeds a filename where BASE64 does not. You will see BASE64 used in encoding digital certificates, in encoding user:password string in an Authorization: header for HTTP. The spec is described in RFC 2045. Don't confuse Base64 with x-www-form-urlencoded which is handled by java.net.URLEncoder.encode/decode or Base64u. Base64 armouring uses only the characters A-Z a-z 0-9 +/=. This makes it suitable for encoding binary data as SQL strings, that will work no matter what the encoding. Unfortunately + / and = all have special meaning in URLs. Base64u gets around this problem. It is a variant on Base64 that uses - _ and * in preference to + / and =, so that it can be used in URLEncoded contexts with or without URLEncoding. Use base64 like this: // Base64 armouring import com.mindprod.base64.Base64; ... // sample byte array to encode byte[] toSend = { (byte)0xfc, (byte)0x0f, (byte)0xc0}; // create encoder object Base64 base64 = new Base64(); base64.setLineLength( 72 ); // default // encoding a byte[] String send = base64.encoder( toSend ); // decoding a byte[] byte[] reconstituted = base64.decoder( sent ); use Base64u the same way: // Base64u armouring import com.mindprod.base64.Base64u; ... // sample byte array to encode byte[] toSend = { (byte)0xfc, (byte)0x0f, (byte)0xc0}; // create encoder object Base64u base64u = new Base64u(); base64u.setLineLength( 72 ); // default // encoding a byte[] String send = base64u.encoder( toSend ); // decoding a byte[] byte[] reconstituted = base64u.decoder( sent ); For an example that starts and ends with a String, see Example.java to run: java.exe com.mindprod.base64.Example